diff --git a/pymongo/helpers.py b/pymongo/helpers.py
index 107e061acf..2fb3ce3372 100644
--- a/pymongo/helpers.py
+++ b/pymongo/helpers.py
@@ -39,6 +39,7 @@
 # "node is recovering" error codes (of which the "node is shutting down"
 # errors are a subset).
 _NOT_MASTER_CODES = frozenset([
+    10058,  # LegacyNotPrimary <=3.2 "not master" error code
     10107,  # NotMaster
     13435,  # NotMasterNoSlaveOk
     11602,  # InterruptedDueToReplStateChange
@@ -148,8 +149,9 @@ def _check_command_response(response, max_wire_version,
             return
 
     # Server is "not master" or "recovering"
-    if code in _NOT_MASTER_CODES:
-        raise NotMasterError(errmsg, response)
+    if code is not None:
+        if code in _NOT_MASTER_CODES:
+            raise NotMasterError(errmsg, response)
     elif "not master" in errmsg or "node is recovering" in errmsg:
         raise NotMasterError(errmsg, response)
 
diff --git a/test/discovery_and_monitoring/errors/non-stale-topologyVersion-greater-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-greater-LegacyNotPrimary.json
new file mode 100644
index 0000000000..e1f33b81bb
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-greater-LegacyNotPrimary.json
@@ -0,0 +1,99 @@
+{
+  "description": "Non-stale topologyVersion greater LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Non-stale topologyVersion greater LegacyNotPrimary error marks server Unknown",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "2"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "2"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/non-stale-topologyVersion-missing-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-missing-LegacyNotPrimary.json
new file mode 100644
index 0000000000..ccaacd1cfe
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-missing-LegacyNotPrimary.json
@@ -0,0 +1,84 @@
+{
+  "description": "Non-stale topologyVersion missing LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Non-stale topologyVersion missing LegacyNotPrimary error marks server Unknown",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/non-stale-topologyVersion-proccessId-changed-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-proccessId-changed-LegacyNotPrimary.json
new file mode 100644
index 0000000000..da36e9b33c
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/non-stale-topologyVersion-proccessId-changed-LegacyNotPrimary.json
@@ -0,0 +1,99 @@
+{
+  "description": "Non-stale topologyVersion proccessId changed LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Non-stale topologyVersion proccessId changed LegacyNotPrimary error marks server Unknown",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000002"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000002"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/post-42-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/post-42-LegacyNotPrimary.json
new file mode 100644
index 0000000000..731da196b5
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/post-42-LegacyNotPrimary.json
@@ -0,0 +1,69 @@
+{
+  "description": "Post-4.2 LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 8
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Post-4.2 LegacyNotPrimary error marks server Unknown",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 8,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/pre-42-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/pre-42-LegacyNotPrimary.json
new file mode 100644
index 0000000000..db5acd718d
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/pre-42-LegacyNotPrimary.json
@@ -0,0 +1,69 @@
+{
+  "description": "Pre-4.2 LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 7
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Pre-4.2 LegacyNotPrimary error marks server Unknown and clears the pool",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 7,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/prefer-error-code.json b/test/discovery_and_monitoring/errors/prefer-error-code.json
new file mode 100644
index 0000000000..486103a457
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/prefer-error-code.json
@@ -0,0 +1,130 @@
+{
+  "description": "Do not check errmsg when code exists",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "errmsg \"not master\" gets ignored when error code exists",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "not master",
+            "code": 1
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "errmsg \"node is recovering\" gets ignored when error code exists",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "node is recovering",
+            "code": 1
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-LegacyNotPrimary.json
new file mode 100644
index 0000000000..2169c4a6fb
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-LegacyNotPrimary.json
@@ -0,0 +1,174 @@
+{
+  "description": "Stale generation LegacyNotPrimary error afterHandshakeCompletes",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Non-stale application network error",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "network"
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Primary A is rediscovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Ignore stale LegacyNotPrimary error (stale generation)",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "generation": 0,
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "2"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-network.json b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-network.json
index 4e11c48eb2..94b8322d2d 100644
--- a/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-network.json
+++ b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-network.json
@@ -1,5 +1,5 @@
 {
-  "description": "Stale generation NotMasterNoSlaveOk error afterHandshakeCompletes",
+  "description": "Stale generation network error afterHandshakeCompletes",
   "uri": "mongodb://a/?replicaSet=rs",
   "phases": [
     {
@@ -124,7 +124,7 @@
       }
     },
     {
-      "description": "Ignore stale NotMasterNoSlaveOk error (stale generation)",
+      "description": "Ignore stale network error (stale generation)",
       "applicationErrors": [
         {
           "address": "a:27017",
diff --git a/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-timeout.json b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-timeout.json
index 27bac32443..490703de90 100644
--- a/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-timeout.json
+++ b/test/discovery_and_monitoring/errors/stale-generation-afterHandshakeCompletes-timeout.json
@@ -1,5 +1,5 @@
 {
-  "description": "Stale generation NotMasterNoSlaveOk error afterHandshakeCompletes",
+  "description": "Stale generation timeout error afterHandshakeCompletes",
   "uri": "mongodb://a/?replicaSet=rs",
   "phases": [
     {
@@ -124,7 +124,7 @@
       }
     },
     {
-      "description": "Ignore stale NotMasterNoSlaveOk error (stale generation)",
+      "description": "Ignore stale timeout error (stale generation)",
       "applicationErrors": [
         {
           "address": "a:27017",
diff --git a/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-LegacyNotPrimary.json
new file mode 100644
index 0000000000..674cb994cd
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-LegacyNotPrimary.json
@@ -0,0 +1,174 @@
+{
+  "description": "Stale generation LegacyNotPrimary error beforeHandshakeCompletes",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Non-stale application network error",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "network"
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "Unknown",
+            "topologyVersion": null,
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetNoPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Primary A is rediscovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Ignore stale LegacyNotPrimary error (stale generation)",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "generation": 0,
+          "when": "beforeHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "2"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 1
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}
diff --git a/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-network.json b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-network.json
index 9734776f22..3e581773eb 100644
--- a/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-network.json
+++ b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-network.json
@@ -1,5 +1,5 @@
 {
-  "description": "Stale generation NotMasterNoSlaveOk error beforeHandshakeCompletes",
+  "description": "Stale generation network error beforeHandshakeCompletes",
   "uri": "mongodb://a/?replicaSet=rs",
   "phases": [
     {
@@ -124,7 +124,7 @@
       }
     },
     {
-      "description": "Ignore stale NotMasterNoSlaveOk error (stale generation)",
+      "description": "Ignore stale network error (stale generation)",
       "applicationErrors": [
         {
           "address": "a:27017",
diff --git a/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-timeout.json b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-timeout.json
index af8730e5ca..24c8c6e507 100644
--- a/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-timeout.json
+++ b/test/discovery_and_monitoring/errors/stale-generation-beforeHandshakeCompletes-timeout.json
@@ -1,5 +1,5 @@
 {
-  "description": "Stale generation NotMasterNoSlaveOk error beforeHandshakeCompletes",
+  "description": "Stale generation timeout error beforeHandshakeCompletes",
   "uri": "mongodb://a/?replicaSet=rs",
   "phases": [
     {
@@ -124,7 +124,7 @@
       }
     },
     {
-      "description": "Ignore stale NotMasterNoSlaveOk error (stale generation)",
+      "description": "Ignore stale timeout error (stale generation)",
       "applicationErrors": [
         {
           "address": "a:27017",
diff --git a/test/discovery_and_monitoring/errors/stale-topologyVersion-LegacyNotPrimary.json b/test/discovery_and_monitoring/errors/stale-topologyVersion-LegacyNotPrimary.json
new file mode 100644
index 0000000000..beee51e666
--- /dev/null
+++ b/test/discovery_and_monitoring/errors/stale-topologyVersion-LegacyNotPrimary.json
@@ -0,0 +1,146 @@
+{
+  "description": "Stale topologyVersion LegacyNotPrimary error",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "description": "Primary A is discovered",
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 9,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Ignore stale LegacyNotPrimary error (topologyVersion less)",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "0"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    },
+    {
+      "description": "Ignore stale LegacyNotPrimary error (topologyVersion equal)",
+      "applicationErrors": [
+        {
+          "address": "a:27017",
+          "when": "afterHandshakeCompletes",
+          "maxWireVersion": 9,
+          "type": "command",
+          "response": {
+            "ok": 0,
+            "errmsg": "LegacyNotPrimary",
+            "code": 10058,
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            }
+          }
+        }
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs",
+            "topologyVersion": {
+              "processId": {
+                "$oid": "000000000000000000000001"
+              },
+              "counter": {
+                "$numberLong": "1"
+              }
+            },
+            "pool": {
+              "generation": 0
+            }
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}