diff --git a/lib/libc/locale/mblocal.h b/lib/libc/locale/mblocal.h
index e424ebe94fe..b4e10985f67 100644
--- a/lib/libc/locale/mblocal.h
+++ b/lib/libc/locale/mblocal.h
@@ -29,6 +29,8 @@
 #ifndef _MBLOCAL_H_
 #define	_MBLOCAL_H_
 
+#include <runetype.h>
+
 /*
  * Rune initialization function prototypes.
  */