diff --git a/pkg/actor/mutation_registry.go b/pkg/actor/mutation_registry.go
index 37130bf..65be2ba 100644
--- a/pkg/actor/mutation_registry.go
+++ b/pkg/actor/mutation_registry.go
@@ -154,7 +154,7 @@ func (r *ProtoMutationRegistry) Apply(grain any, msg ...proto.Message) error {
 	}
 
 	for _, m := range msg {
-		rt := indirectType(reflect.TypeOf(msg))
+		rt := indirectType(reflect.TypeOf(m))
 		r.mutationRegistryMu.RLock()
 		entry, ok := r.mutationRegistry[rt]
 		r.mutationRegistryMu.RUnlock()