diff --git a/util/systemc/sc_module.cc b/util/systemc/sc_module.cc
--- a/util/systemc/sc_module.cc
+++ b/util/systemc/sc_module.cc
@@ -140,6 +140,7 @@
 Module::serviceAsyncEvent()
 {
     EventQueue *eventq = getEventQueue(0);
+    std::lock_guard<EventQueue> lock(*eventq);
 
     assert(async_event);