diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index e95c96220b8..1bb0eaa991a 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -421,7 +421,7 @@ namespace ts {
             trace(host, Diagnostics.Resolving_module_0_from_1, moduleName, containingFile);
         }
         const containingDirectory = getDirectoryPath(containingFile);
-        let perFolderCache = cache && cache.getOrCreateCacheForDirectory(containingDirectory);
+        const perFolderCache = cache && cache.getOrCreateCacheForDirectory(containingDirectory);
         let result = perFolderCache && perFolderCache[moduleName];
 
         if (result) {