diff --git a/__mocks__/gatsby-plugin-firebase/database/reference.js b/__mocks__/gatsby-plugin-firebase/database/reference.js
index 6d422314..ea04ee40 100644
--- a/__mocks__/gatsby-plugin-firebase/database/reference.js
+++ b/__mocks__/gatsby-plugin-firebase/database/reference.js
@@ -175,6 +175,8 @@ class Reference {
     if (eventType === DatabaseConstants.valueEventType) {
       this.triggerEventCallback(eventType);
     }
+
+    return callback;
   }
 
   async once(eventType) {