diff --git a/.changeset/purple-dryers-peel.md b/.changeset/purple-dryers-peel.md
new file mode 100644
index 000000000..fc385f191
--- /dev/null
+++ b/.changeset/purple-dryers-peel.md
@@ -0,0 +1,6 @@
+---
+'@accounts/mongo-password': minor
+'@accounts/mongo-sessions': minor
+---
+
+MongoDB 4.X support for Meteor@2.5.1 - Mongo.createUser and Mongo.createSession bugfixes
diff --git a/packages/database-mongo-password/src/mongo-password.ts b/packages/database-mongo-password/src/mongo-password.ts
index bbf51a3c4..34dd1b7eb 100644
--- a/packages/database-mongo-password/src/mongo-password.ts
+++ b/packages/database-mongo-password/src/mongo-password.ts
@@ -149,8 +149,9 @@ export class MongoServicePassword implements DatabaseInterfaceServicePassword {
       user._id = this.options.idProvider();
     }
     const ret = await this.userCollection.insertOne(user);
+    
     // keep ret.ops for compatibility with MongoDB 3.X, version 4.X uses insertedId
-    return ((ret.insertedId ?? ret.ops[0]._id) as ObjectID).toString();
+    return ((ret.insertedId ? ret.insertedId : ret.ops[0]._id) as ObjectID).toString();
   }
 
   /**
diff --git a/packages/database-mongo-sessions/src/mongo-sessions.ts b/packages/database-mongo-sessions/src/mongo-sessions.ts
index 5f61c75d8..9ac7945e5 100644
--- a/packages/database-mongo-sessions/src/mongo-sessions.ts
+++ b/packages/database-mongo-sessions/src/mongo-sessions.ts
@@ -124,7 +124,8 @@ export class MongoSessions implements DatabaseInterfaceSessions {
 
     const ret = await this.sessionCollection.insertOne(session);
     // keep ret.ops for compatibility with MongoDB 3.X, version 4.X uses insertedId
-    return ((ret.insertedId ?? ret.ops[0]._id) as ObjectID).toString();
+    return ((ret.insertedId ? ret.insertedId : ret.ops[0]._id) as ObjectID).toString();
+
   }
 
   /**