diff --git a/src/server/server.ts b/src/server/server.ts
index fd4fcb87bbf..d828a717a41 100644
--- a/src/server/server.ts
+++ b/src/server/server.ts
@@ -596,7 +596,7 @@ namespace ts.server {
     }
 
     sys.require = (initialDir: string, moduleName: string): RequireResult => {
-        const result = nodeModuleNameResolver(moduleName, initialDir + "/program.ts", { moduleResolution: ts.ModuleResolutionKind.NodeJs, allowJs: true }, sys, undefined, /*jsOnly*/ true);
+        const result = nodeModuleNameResolverWorker(moduleName, initialDir + "/program.ts", { moduleResolution: ts.ModuleResolutionKind.NodeJs, allowJs: true }, sys, undefined, /*jsOnly*/ true);
         try {
             return { module: require(result.resolvedModule.resolvedFileName), error: undefined };
         }