diff --git a/lib/stdlib/mbstowcs.c b/lib/stdlib/mbstowcs.c
index 0820c1ef..543464b3 100644
--- a/lib/stdlib/mbstowcs.c
+++ b/lib/stdlib/mbstowcs.c
@@ -19,6 +19,7 @@
  */
 
 #include <mes/lib.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>