diff --git a/stralloc/stralloc_catm_internal.c b/stralloc/stralloc_catm_internal.c
index 65ead7a..1da5377 100644
--- a/stralloc/stralloc_catm_internal.c
+++ b/stralloc/stralloc_catm_internal.c
@@ -1,4 +1,5 @@
 #include <stdarg.h>
+#include <string.h>
 #include "stralloc.h"
 
 int stralloc_catm_internal(stralloc* sa, ...) {