diff --git a/Tests/CTestTestUpload/sleep.c b/Tests/CTestTestUpload/sleep.c
index b9b6e897bc..2d69f7f5a8 100644
--- a/Tests/CTestTestUpload/sleep.c
+++ b/Tests/CTestTestUpload/sleep.c
@@ -1,3 +1,5 @@
+#include <stdlib.h>
+
 #if defined(_WIN32)
 #  include <windows.h>
 #else