diff --git a/lib/modules/firestore/CollectionReference.js b/lib/modules/firestore/CollectionReference.js
index 7b0794bf..87598b57 100644
--- a/lib/modules/firestore/CollectionReference.js
+++ b/lib/modules/firestore/CollectionReference.js
@@ -6,9 +6,11 @@ import DocumentReference from './DocumentReference';
 import Query from './Query';
 import { firestoreAutoId } from '../../utils';
 
+import type DocumentSnapshot from './DocumentSnapshot';
 import type Firestore from './';
 import type { FirestoreQueryDirection, FirestoreQueryOperator } from '../../types';
 import type Path from './Path';
+import type { Observer, QueryListenOptions } from './Query';
 import type QuerySnapshot from './QuerySnapshot';
 
 /**
@@ -19,13 +21,13 @@ export default class CollectionReference {
   _firestore: Firestore;
   _query: Query;
 
-  constructor(firestore: Object, collectionPath: Path) {
+  constructor(firestore: Firestore, collectionPath: Path) {
     this._collectionPath = collectionPath;
     this._firestore = firestore;
     this._query = new Query(firestore, collectionPath);
   }
 
-  get firestore(): Object {
+  get firestore(): Firestore {
     return this._firestore;
   }
 
@@ -56,36 +58,40 @@ export default class CollectionReference {
   }
 
   // From Query
-  endAt(fieldValues: any): Query {
-    return this._query.endAt(fieldValues);
+  endAt(...snapshotOrVarArgs: any[]): Query {
+    return this._query.endAt(snapshotOrVarArgs);
   }
 
-  endBefore(fieldValues: any): Query {
-    return this._query.endBefore(fieldValues);
+  endBefore(...snapshotOrVarArgs: any[]): Query {
+    return this._query.endBefore(snapshotOrVarArgs);
   }
 
   get(): Promise<QuerySnapshot> {
     return this._query.get();
   }
 
-  limit(n: number): Query {
-    return this._query.limit(n);
+  limit(limit: number): Query {
+    return this._query.limit(limit);
   }
 
-  onSnapshot(onNext: () => any, onError?: () => any): () => void {
-    return this._query.onSnapshot(onNext, onError);
+  onSnapshot(
+    optionsOrObserverOrOnNext: QueryListenOptions | Observer | (DocumentSnapshot) => void,
+    observerOrOnNextOrOnError?: Observer | (DocumentSnapshot) => void | (Object) => void,
+    onError?: (Object) => void,
+  ): () => void {
+    return this._query.onSnapshot(optionsOrObserverOrOnNext, observerOrOnNextOrOnError, onError);
   }
 
   orderBy(fieldPath: string, directionStr?: FirestoreQueryDirection): Query {
     return this._query.orderBy(fieldPath, directionStr);
   }
 
-  startAfter(fieldValues: any): Query {
-    return this._query.startAfter(fieldValues);
+  startAfter(...snapshotOrVarArgs: any[]): Query {
+    return this._query.startAfter(snapshotOrVarArgs);
   }
 
-  startAt(fieldValues: any): Query {
-    return this._query.startAt(fieldValues);
+  startAt(...snapshotOrVarArgs: any[]): Query {
+    return this._query.startAt(snapshotOrVarArgs);
   }
 
   where(fieldPath: string, opStr: FirestoreQueryOperator, value: any): Query {
diff --git a/lib/modules/firestore/DocumentReference.js b/lib/modules/firestore/DocumentReference.js
index b47c88c6..97d7c4ae 100644
--- a/lib/modules/firestore/DocumentReference.js
+++ b/lib/modules/firestore/DocumentReference.js
@@ -163,7 +163,7 @@ export default class DocumentReference {
       .documentSet(this.path, nativeData, writeOptions);
   }
 
-  update(...args: Array<any>): Promise<void> {
+  update(...args: any[]): Promise<void> {
     let data = {};
     if (args.length === 1) {
       if (!isObject(args[0])) {
diff --git a/lib/modules/firestore/Query.js b/lib/modules/firestore/Query.js
index 507399ff..af11cae4 100644
--- a/lib/modules/firestore/Query.js
+++ b/lib/modules/firestore/Query.js
@@ -45,12 +45,13 @@ type QueryOptions = {
   startAfter?: any[],
   startAt?: any[],
 }
-type QueryListenOptions = {
+
+export type QueryListenOptions = {
   includeDocumentMetadataChanges: boolean,
   includeQueryMetadataChanges: boolean,
 }
 
-type Observer = {
+export type Observer = {
   next: (DocumentSnapshot) => void,
   error?: (Object) => void,
 }
@@ -81,7 +82,7 @@ export default class Query {
     this._referencePath = path;
   }
 
-  get firestore(): Object {
+  get firestore(): Firestore {
     return this._firestore;
   }