diff --git a/src/server/protocol.d.ts b/src/server/protocol.d.ts
index 3a669753323..b8207570ea2 100644
--- a/src/server/protocol.d.ts
+++ b/src/server/protocol.d.ts
@@ -469,7 +469,7 @@ declare namespace ts.server.protocol {
         placeOpenBraceOnNewLineForControlBlocks?: boolean;
 
         /** Index operator */
-        [key: string] : string | number | boolean;
+        [key: string]: string | number | boolean;
     }
 
     /**