diff --git a/lib/utils/locker.js b/lib/utils/locker.js
index 343dd270..82f6fb20 100644
--- a/lib/utils/locker.js
+++ b/lib/utils/locker.js
@@ -86,7 +86,7 @@ Locker.prototype.lock = function lock(arg1, arg2) {
 
   if (force) {
     assert(this.busy);
-    return Promise.resolve(null);
+    return Promise.resolve(utils.nop);
   }
 
   if (this.busy) {
@@ -220,7 +220,7 @@ MappedLock.prototype.lock = function lock(key, force) {
 
   if (force || key == null) {
     assert(key == null || this.busy[key]);
-    return Promise.resolve(null);
+    return Promise.resolve(utils.nop);
   }
 
   if (this.busy[key]) {