diff --git a/MultilineGreyText/RefactLanguageClient.cs b/MultilineGreyText/RefactLanguageClient.cs
index f8655dc..f5cca46 100644
--- a/MultilineGreyText/RefactLanguageClient.cs
+++ b/MultilineGreyText/RefactLanguageClient.cs
@@ -248,7 +248,7 @@ public async Task<string> RefactCompletion(PropertyCollection props, String file
                 return null;
             }
             if (!ContainsFile(fileUri)){
-                return;
+                return null;
             }
             //catching server errors
             try{