diff --git a/src/common/tuklib_mbstr_width.c b/src/common/tuklib_mbstr_width.c
index 4bbe9647..2eab2341 100644
--- a/src/common/tuklib_mbstr_width.c
+++ b/src/common/tuklib_mbstr_width.c
@@ -11,6 +11,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "tuklib_mbstr.h"
+#include <string.h>
 
 #if defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH)
 #	include <wchar.h>