diff --git a/packages/mongo/oplog_tailing.ts b/packages/mongo/oplog_tailing.ts
index fe99db2833..440339fa6f 100644
--- a/packages/mongo/oplog_tailing.ts
+++ b/packages/mongo/oplog_tailing.ts
@@ -226,14 +226,9 @@ export class OplogHandle {
     );
 
     try {
-      const isMasterDoc = await new Promise<any>((resolve, reject) => {
-        this._oplogLastEntryConnection!.db
-          .admin()
-          .command({ ismaster: 1 }, (err: Error | null, result: any) => {
-            if (err) reject(err);
-            else resolve(result);
-          });
-      });
+      const isMasterDoc = await this._oplogLastEntryConnection!.db
+        .admin()
+        .command({ ismaster: 1 });
 
       if (!(isMasterDoc && isMasterDoc.setName)) {
         throw new Error("$MONGO_OPLOG_URL must be set to the 'local' database of a Mongo replica set");
@@ -426,4 +421,4 @@ export function idForOp(op: OplogEntry): string {
   } else {
     throw Error("Unknown op: " + JSON.stringify(op));
   }
-}
\ No newline at end of file
+}
diff --git a/packages/mongo/tests/observe_changes_tests.js b/packages/mongo/tests/observe_changes_tests.js
index 0fe94d2ebf..8974bd7b22 100644
--- a/packages/mongo/tests/observe_changes_tests.js
+++ b/packages/mongo/tests/observe_changes_tests.js
@@ -495,6 +495,7 @@ if (Meteor.isServer) {
       self.handle = await cursor.observeChanges({
         added: function(id, fields) {
           self.xs.push(fields.x);
+          console.log('self.expects.length', self.expects);
           test.notEqual(self.expects.length, 0);
           self.expects.pop()();
         },