diff --git a/src/libCom/test/epicsTimeTest.cpp b/src/libCom/test/epicsTimeTest.cpp
index 5d4c60f91..07fd97fe0 100644
--- a/src/libCom/test/epicsTimeTest.cpp
+++ b/src/libCom/test/epicsTimeTest.cpp
@@ -9,7 +9,7 @@
 /*
  * Authors: Jeff HIll and Marty Kraimer
  */
-#include <stddef>
+#include <cstddef>
 #include <cstdio>
 #include <ctime>
 #include <cmath>