diff --git a/rosidl_generator_java/resource/msg.cpp.em b/rosidl_generator_java/resource/msg.cpp.em
index 8553bfcb..84c4bb64 100644
--- a/rosidl_generator_java/resource/msg.cpp.em
+++ b/rosidl_generator_java/resource/msg.cpp.em
@@ -519,6 +519,7 @@ if value_method:
 
 JNIEXPORT void JNICALL JNI_OnUnload(JavaVM * vm, void *)
 {
+  (void)vm;
   assert(g_vm != nullptr);
   assert(g_vm == vm);