diff --git a/reactos/tools/unicode/string.c b/reactos/tools/unicode/string.c
index 6afb89967e3..d9f6144bb9a 100644
--- a/reactos/tools/unicode/string.c
+++ b/reactos/tools/unicode/string.c
@@ -21,6 +21,7 @@
 #include <assert.h>
 #include <limits.h>
 #include <stdio.h>
+#include <string.h>
 
 #define WINE_UNICODE_INLINE  /* nothing */
 #include "wine/unicode.h"