diff --git a/firebase.d.ts b/firebase.d.ts
index c5e3a81..8e44ac6 100644
--- a/firebase.d.ts
+++ b/firebase.d.ts
@@ -11,7 +11,7 @@ declare namespace firebase {
             TIMESTAMP,
         }
 
-        export function enableLogging(enable: boolean);
+        export function enableLogging(enable: boolean): void;
     }