diff --git a/firebase-firestore/src/test/java/com/google/firebase/firestore/spec/SpecTestCase.java b/firebase-firestore/src/test/java/com/google/firebase/firestore/spec/SpecTestCase.java
index 8fa7375ebeb..1b2dcc4c66e 100644
--- a/firebase-firestore/src/test/java/com/google/firebase/firestore/spec/SpecTestCase.java
+++ b/firebase-firestore/src/test/java/com/google/firebase/firestore/spec/SpecTestCase.java
@@ -478,6 +478,18 @@ private List<Integer> parseIntList(@Nullable JSONArray arr) throws JSONException
     return result;
   }
 
+  /** Deeply parses a JSONArray into a List<String>. */
+  private List<String> parseStringList(@Nullable JSONArray arr) throws JSONException {
+    List<String> result = new ArrayList<>();
+    if (arr == null) {
+      return result;
+    }
+    for (int i = 0; i < arr.length(); ++i) {
+      result.add(arr.getString(i));
+    }
+    return result;
+  }
+
   //
   // Methods for doing the steps of the spec test.
   //
@@ -665,15 +677,14 @@ private void doWatchEntity(JSONObject watchEntity) throws Exception {
     }
   }
 
-  private void doWatchFilter(JSONArray watchFilter) throws Exception {
-    List<Integer> targets = parseIntList(watchFilter.getJSONArray(0));
+  private void doWatchFilter(JSONObject watchFilter) throws Exception {
+    List<String> keys = parseStringList(watchFilter.getJSONArray("keys"));
+    List<Integer> targets = parseIntList(watchFilter.getJSONArray("targetIds"));
     Assert.hardAssert(
         targets.size() == 1, "ExistenceFilters currently support exactly one target only.");
 
-    int keyCount = watchFilter.length() == 0 ? 0 : watchFilter.length() - 1;
-
     // TODO: extend this with different existence filters over time.
-    ExistenceFilter filter = new ExistenceFilter(keyCount);
+    ExistenceFilter filter = new ExistenceFilter(keys.size());
     ExistenceFilterWatchChange change = new ExistenceFilterWatchChange(targets.get(0), filter);
     writeWatchChange(change, SnapshotVersion.NONE);
   }
@@ -850,7 +861,7 @@ private void doStep(JSONObject step) throws Exception {
     } else if (step.has("watchEntity")) {
       doWatchEntity(step.getJSONObject("watchEntity"));
     } else if (step.has("watchFilter")) {
-      doWatchFilter(step.getJSONArray("watchFilter"));
+      doWatchFilter(step.getJSONObject("watchFilter"));
     } else if (step.has("watchReset")) {
       doWatchReset(step.getJSONArray("watchReset"));
     } else if (step.has("watchSnapshot")) {
diff --git a/firebase-firestore/src/test/resources/json/existence_filter_spec_test.json b/firebase-firestore/src/test/resources/json/existence_filter_spec_test.json
index c0be6b22cfb..0a4ecb48201 100644
--- a/firebase-firestore/src/test/resources/json/existence_filter_spec_test.json
+++ b/firebase-firestore/src/test/resources/json/existence_filter_spec_test.json
@@ -132,12 +132,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -366,13 +368,15 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1",
+            "collection/2"
           ],
-          "collection/1",
-          "collection/2"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchEntity": {
@@ -729,11 +733,13 @@
         }
       },
       {
-        "watchFilter": [
-          [
+        "watchFilter": {
+          "keys": [
+          ],
+          "targetIds": [
             2
           ]
-        ]
+        }
       },
       {
         "watchRemove": {
@@ -910,12 +916,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -1203,12 +1211,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -1313,12 +1323,14 @@
         }
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -1489,12 +1501,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -1846,12 +1860,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
@@ -2149,11 +2165,13 @@
         ]
       },
       {
-        "watchFilter": [
-          [
+        "watchFilter": {
+          "keys": [
+          ],
+          "targetIds": [
             2
           ]
-        ]
+        }
       },
       {
         "watchSnapshot": {
@@ -2265,12 +2283,14 @@
         ]
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/1"
           ],
-          "collection/1"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
diff --git a/firebase-firestore/src/test/resources/json/limbo_spec_test.json b/firebase-firestore/src/test/resources/json/limbo_spec_test.json
index c4c179fd8ba..8172a189689 100644
--- a/firebase-firestore/src/test/resources/json/limbo_spec_test.json
+++ b/firebase-firestore/src/test/resources/json/limbo_spec_test.json
@@ -3445,11 +3445,13 @@
         ]
       },
       {
-        "watchFilter": [
-          [
+        "watchFilter": {
+          "keys": [
+          ],
+          "targetIds": [
             1
           ]
-        ]
+        }
       },
       {
         "watchCurrent": [
@@ -8201,15 +8203,16 @@
         }
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/b1",
+            "collection/b2",
+            "collection/b3"
           ],
-          "collection/b1",
-          "collection/b2",
-          "collection/b3"
-        ]
-
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {
diff --git a/firebase-firestore/src/test/resources/json/limit_spec_test.json b/firebase-firestore/src/test/resources/json/limit_spec_test.json
index 37ec88b11c0..257c53eeb4c 100644
--- a/firebase-firestore/src/test/resources/json/limit_spec_test.json
+++ b/firebase-firestore/src/test/resources/json/limit_spec_test.json
@@ -5611,12 +5611,14 @@
         }
       },
       {
-        "watchFilter": [
-          [
-            2
+        "watchFilter": {
+          "keys": [
+            "collection/b"
           ],
-          "collection/b"
-        ]
+          "targetIds": [
+            2
+          ]
+        }
       },
       {
         "watchSnapshot": {