diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 73c92eff547..834f451df80 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -1415,7 +1415,7 @@ namespace ts {
     }
 
     /** Remove the *first* element satisfying `predicate`. */
-    export function unorderedRemoveFirstItemWhere<T>(array: T[], predicate: (element: T) => boolean): void {
+    function unorderedRemoveFirstItemWhere<T>(array: T[], predicate: (element: T) => boolean): void {
         for (let i = 0; i < array.length; i++) {
             if (predicate(array[i])) {
                 unorderedRemoveItemAt(array, i);
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index b02e4d81cd3..0c491ad349e 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -209,12 +209,13 @@ namespace ts {
         watchDirectory(directoryName: string, callback: DirectoryWatcherCallback, recursive: boolean): DirectoryWatcher {
             const path = this.toPath(directoryName);
             const callbacks = lookUp(this.watchedDirectories, path) || (this.watchedDirectories[path] = []);
-            callbacks.push({ cb: callback, recursive });
+            const cbWithRecursive = { cb: callback, recursive };
+            callbacks.push(cbWithRecursive);
             return {
                 referenceCount: 0,
                 directoryName,
                 close: () => {
-                    unorderedRemoveFirstItemWhere(callbacks, cb => cb.cb === callback);
+                    unorderedRemoveItem(cbWithRecursive, callbacks);
                     if (!callbacks.length) {
                         delete this.watchedDirectories[path];
                     }