diff --git a/test_regress/t/TestSimulator.h b/test_regress/t/TestSimulator.h
index 3ac4307e1..5c49404f4 100644
--- a/test_regress/t/TestSimulator.h
+++ b/test_regress/t/TestSimulator.h
@@ -11,6 +11,7 @@
 
 #include "vpi_user.h"
 
+#include <cstring>
 #include <sstream>
 
 class TestSimulator {