diff --git a/packages/analytics/src/index.ts b/packages/analytics/src/index.ts
index 0fc2a8e2b0a..69e024c3311 100644
--- a/packages/analytics/src/index.ts
+++ b/packages/analytics/src/index.ts
@@ -82,7 +82,7 @@ function registerAnalytics(): void {
       };
     } catch (e) {
       throw ERROR_FACTORY.create(AnalyticsError.INTEROP_COMPONENT_REG_FAILED, {
-        reason: e
+        reason: e as Error
       });
     }
   }
diff --git a/packages/auth/src/core/auth/middleware.ts b/packages/auth/src/core/auth/middleware.ts
index 01fe8e40168..2f5fa3a5065 100644
--- a/packages/auth/src/core/auth/middleware.ts
+++ b/packages/auth/src/core/auth/middleware.ts
@@ -87,7 +87,7 @@ export class AuthMiddlewareQueue {
       }
 
       throw this.auth._errorFactory.create(
-        AuthErrorCode.LOGIN_BLOCKED, { originalMessage: e.message });
+        AuthErrorCode.LOGIN_BLOCKED, { originalMessage: (e as Error)?.message });
     }
   }
-}
\ No newline at end of file
+}
diff --git a/packages/auth/test/integration/flows/phone.test.ts b/packages/auth/test/integration/flows/phone.test.ts
index 2711292d046..389fb9e5947 100644
--- a/packages/auth/test/integration/flows/phone.test.ts
+++ b/packages/auth/test/integration/flows/phone.test.ts
@@ -294,7 +294,7 @@ describe('Integration test: phone auth', () => {
           )
         );
       } catch (e) {
-        error = e;
+         error = e as FirebaseError;
       }
 
       expect(error!.customData!.phoneNumber).to.eq(PHONE_A.phoneNumber);
diff --git a/packages/firestore-compat/src/api/database.ts b/packages/firestore-compat/src/api/database.ts
index bf5715ee43d..f4e63c09d77 100644
--- a/packages/firestore-compat/src/api/database.ts
+++ b/packages/firestore-compat/src/api/database.ts
@@ -297,7 +297,11 @@ export class Firestore
         collection(this._delegate, pathString)
       );
     } catch (e) {
-      throw replaceFunctionName(e, 'collection()', 'Firestore.collection()');
+      throw replaceFunctionName(
+        e as Error,
+        'collection()',
+        'Firestore.collection()'
+      );
     }
   }
 
@@ -305,7 +309,7 @@ export class Firestore
     try {
       return new DocumentReference(this, doc(this._delegate, pathString));
     } catch (e) {
-      throw replaceFunctionName(e, 'doc()', 'Firestore.doc()');
+      throw replaceFunctionName(e as Error, 'doc()', 'Firestore.doc()');
     }
   }
 
@@ -314,7 +318,7 @@ export class Firestore
       return new Query(this, collectionGroup(this._delegate, collectionId));
     } catch (e) {
       throw replaceFunctionName(
-        e,
+        e as Error,
         'collectionGroup()',
         'Firestore.collectionGroup()'
       );
@@ -687,7 +691,7 @@ export class DocumentReference<T = PublicDocumentData>
       );
     } catch (e) {
       throw replaceFunctionName(
-        e,
+        e as Error,
         'collection()',
         'DocumentReference.collection()'
       );
@@ -718,7 +722,11 @@ export class DocumentReference<T = PublicDocumentData>
         return setDoc(this._delegate, value as WithFieldValue<T>);
       }
     } catch (e) {
-      throw replaceFunctionName(e, 'setDoc()', 'DocumentReference.set()');
+      throw replaceFunctionName(
+        e as Error,
+        'setDoc()',
+        'DocumentReference.set()'
+      );
     }
   }
 
@@ -745,7 +753,11 @@ export class DocumentReference<T = PublicDocumentData>
         );
       }
     } catch (e) {
-      throw replaceFunctionName(e, 'updateDoc()', 'DocumentReference.update()');
+      throw replaceFunctionName(
+        e as Error,
+        'updateDoc()',
+        'DocumentReference.update()'
+      );
     }
   }
 
@@ -991,7 +1003,11 @@ export class Query<T = PublicDocumentData>
         query(this._delegate, where(fieldPath as string, opStr, value))
       );
     } catch (e) {
-      throw replaceFunctionName(e, /(orderBy|where)\(\)/, 'Query.$1()');
+      throw replaceFunctionName(
+        e as Error,
+        /(orderBy|where)\(\)/,
+        'Query.$1()'
+      );
     }
   }
 
@@ -1008,7 +1024,11 @@ export class Query<T = PublicDocumentData>
         query(this._delegate, orderBy(fieldPath as string, directionStr))
       );
     } catch (e) {
-      throw replaceFunctionName(e, /(orderBy|where)\(\)/, 'Query.$1()');
+      throw replaceFunctionName(
+        e as Error,
+        /(orderBy|where)\(\)/,
+        'Query.$1()'
+      );
     }
   }
 
@@ -1016,7 +1036,7 @@ export class Query<T = PublicDocumentData>
     try {
       return new Query<T>(this.firestore, query(this._delegate, limit(n)));
     } catch (e) {
-      throw replaceFunctionName(e, 'limit()', 'Query.limit()');
+      throw replaceFunctionName(e as Error, 'limit()', 'Query.limit()');
     }
   }
 
@@ -1027,7 +1047,11 @@ export class Query<T = PublicDocumentData>
         query(this._delegate, limitToLast(n))
       );
     } catch (e) {
-      throw replaceFunctionName(e, 'limitToLast()', 'Query.limitToLast()');
+      throw replaceFunctionName(
+        e as Error,
+        'limitToLast()',
+        'Query.limitToLast()'
+      );
     }
   }
 
@@ -1035,7 +1059,7 @@ export class Query<T = PublicDocumentData>
     try {
       return new Query(this.firestore, query(this._delegate, startAt(...args)));
     } catch (e) {
-      throw replaceFunctionName(e, 'startAt()', 'Query.startAt()');
+      throw replaceFunctionName(e as Error, 'startAt()', 'Query.startAt()');
     }
   }
 
@@ -1046,7 +1070,11 @@ export class Query<T = PublicDocumentData>
         query(this._delegate, startAfter(...args))
       );
     } catch (e) {
-      throw replaceFunctionName(e, 'startAfter()', 'Query.startAfter()');
+      throw replaceFunctionName(
+        e as Error,
+        'startAfter()',
+        'Query.startAfter()'
+      );
     }
   }
 
@@ -1057,7 +1085,7 @@ export class Query<T = PublicDocumentData>
         query(this._delegate, endBefore(...args))
       );
     } catch (e) {
-      throw replaceFunctionName(e, 'endBefore()', 'Query.endBefore()');
+      throw replaceFunctionName(e as Error, 'endBefore()', 'Query.endBefore()');
     }
   }
 
@@ -1065,7 +1093,7 @@ export class Query<T = PublicDocumentData>
     try {
       return new Query(this.firestore, query(this._delegate, endAt(...args)));
     } catch (e) {
-      throw replaceFunctionName(e, 'endAt()', 'Query.endAt()');
+      throw replaceFunctionName(e as Error, 'endAt()', 'Query.endAt()');
     }
   }
 
@@ -1265,7 +1293,11 @@ export class CollectionReference<T = PublicDocumentData>
         );
       }
     } catch (e) {
-      throw replaceFunctionName(e, 'doc()', 'CollectionReference.doc()');
+      throw replaceFunctionName(
+        e as Error,
+        'doc()',
+        'CollectionReference.doc()'
+      );
     }
   }
 
diff --git a/packages/firestore/src/core/event_manager.ts b/packages/firestore/src/core/event_manager.ts
index 33924b45923..ecce1109150 100644
--- a/packages/firestore/src/core/event_manager.ts
+++ b/packages/firestore/src/core/event_manager.ts
@@ -97,7 +97,7 @@ export async function eventManagerListen(
       queryInfo.viewSnap = await eventManagerImpl.onListen(query);
     } catch (e) {
       const firestoreError = wrapInUserErrorIfRecoverable(
-        e,
+        e as Error,
         `Initialization of query '${stringifyQuery(listener.query)}' failed`
       );
       listener.onError(firestoreError);
diff --git a/packages/messaging/src/helpers/registerDefaultSw.ts b/packages/messaging/src/helpers/registerDefaultSw.ts
index 2d929596c68..239e6ed8244 100644
--- a/packages/messaging/src/helpers/registerDefaultSw.ts
+++ b/packages/messaging/src/helpers/registerDefaultSw.ts
@@ -41,7 +41,7 @@ export async function registerDefaultSw(
     });
   } catch (e) {
     throw ERROR_FACTORY.create(ErrorCode.FAILED_DEFAULT_REGISTRATION, {
-      browserErrorMessage: e.message
+      browserErrorMessage: (e as Error)?.message
     });
   }
 }
diff --git a/repo-scripts/api-documenter/src/plugin/PluginLoader.ts b/repo-scripts/api-documenter/src/plugin/PluginLoader.ts
index fc02d35190d..3bf868c86e2 100644
--- a/repo-scripts/api-documenter/src/plugin/PluginLoader.ts
+++ b/repo-scripts/api-documenter/src/plugin/PluginLoader.ts
@@ -124,7 +124,8 @@ export class PluginLoader {
               );
             } catch (e) {
               throw new Error(
-                `Failed to construct feature subclass:\n` + e.toString()
+                `Failed to construct feature subclass:\n` +
+                  (e as Error)?.toString()
               );
             }
             if (
@@ -140,7 +141,7 @@ export class PluginLoader {
             } catch (e) {
               throw new Error(
                 'Error occurred during the onInitialized() event: ' +
-                  e.toString()
+                  (e as Error)?.toString()
               );
             }
 
@@ -153,7 +154,8 @@ export class PluginLoader {
         }
       } catch (e) {
         throw new Error(
-          `Error loading plugin ${configPlugin.packageName}: ` + e.message
+          `Error loading plugin ${configPlugin.packageName}: ` +
+            (e as Error)?.message
         );
       }
     }
diff --git a/scripts/ci/check_changeset.ts b/scripts/ci/check_changeset.ts
index d9d92688ebf..b5c8fd7e075 100644
--- a/scripts/ci/check_changeset.ts
+++ b/scripts/ci/check_changeset.ts
@@ -126,10 +126,11 @@ async function main() {
     await exec(`yarn changeset status`);
     console.log(`::set-output name=BLOCKING_FAILURE::false`);
   } catch (e) {
-    if (e.message.match('No changesets present')) {
+    const error = e as Error;
+    if (error.message.match('No changesets present')) {
       console.log(`::set-output name=BLOCKING_FAILURE::false`);
     } else {
-      const messageLines = e.message.replace(/🦋  error /g, '').split('\n');
+      const messageLines = error.message.replace(/🦋  error /g, '').split('\n');
       let formattedStatusError =
         '- Changeset formatting error in following file:%0A';
       formattedStatusError += '    ```%0A';