diff --git a/utils/system_test/main.cpp b/utils/system_test/main.cpp
index 5ebb7860..6ae946f9 100755
--- a/utils/system_test/main.cpp
+++ b/utils/system_test/main.cpp
@@ -19,7 +19,9 @@
 
 #include "pip.h"
 #include "pisystemtests.h"
-
+#ifdef CC_GCC
+#  include <unistd.h>
+#endif
 
 int main(int argc, char * argv[]) {
 #if defined(WINDOWS) || defined(MAC_OS)