diff --git a/proc.cpp b/proc.cpp
index c8d6c598c..f444a7be1 100644
--- a/proc.cpp
+++ b/proc.cpp
@@ -205,6 +205,7 @@ void proc_destroy()
 
 void proc_set_last_status(int s)
 {
+    ASSERT_IS_MAIN_THREAD();
     last_status = s;
 }