diff --git a/src/locker.js b/src/locker.js
index a2e84b677..ff71238df 100644
--- a/src/locker.js
+++ b/src/locker.js
@@ -55,7 +55,7 @@ Locker.prototype.recursiveLock = function (operation) {
 Locker.prototype.unlock = function (operation) {
     assert.strictEqual(typeof operation, 'string');
 
-    if (this._operation !== operation) throw BoxError(BoxError.BAD_STATE, 'Mismatched unlock. Current lock is for ' + this._operation); // throw because this is a programming error
+    if (this._operation !== operation) throw new BoxError(BoxError.BAD_STATE, 'Mismatched unlock. Current lock is for ' + this._operation); // throw because this is a programming error
 
     if (--this._lockDepth === 0) {
         debug('Released : %s', this._operation);