diff --git a/Utilities/cmlibrhash/librhash/rhash.c b/Utilities/cmlibrhash/librhash/rhash.c
index ad6249b177..34e1eb3058 100644
--- a/Utilities/cmlibrhash/librhash/rhash.c
+++ b/Utilities/cmlibrhash/librhash/rhash.c
@@ -18,6 +18,8 @@
 #define _LARGEFILE64_SOURCE
 #define _FILE_OFFSET_BITS 64
 
+#include "ustd.h"   /* Need this first within CMake.  */
+
 #include <string.h> /* memset() */
 #include <stdlib.h> /* free() */
 #include <stddef.h> /* ptrdiff_t */