diff --git a/lib/controller.js b/lib/controller.js
index ba3288b77..e472f4021 100644
--- a/lib/controller.js
+++ b/lib/controller.js
@@ -389,7 +389,7 @@ class Controller {
         if (cacheState) {
             // Add cached state to payload
             if (this.stateCache[deviceID]) {
-                payload = objectAssignDeep(this.stateCache[deviceID], payload);
+                payload = objectAssignDeep.noMutate(this.stateCache[deviceID], payload);
             }
 
             // Update state cache with new state.