diff --git a/packages/vulcan-lib/lib/server/mutators.js b/packages/vulcan-lib/lib/server/mutators.js
index 2d348efd3..a64441583 100644
--- a/packages/vulcan-lib/lib/server/mutators.js
+++ b/packages/vulcan-lib/lib/server/mutators.js
@@ -578,7 +578,7 @@ const startDebugMutator = (name, action, properties) => {
   });
 };
 
-const endDebugMutator = (name, action, properties) => {
+const endDebugMutator = (name, action, properties = {}) => {
   Object.keys(properties).forEach(p => {
     debug(`// ${p}: `, properties[p]);
   });