diff --git a/lib/libarchive/archive_string.h b/lib/libarchive/archive_string.h
index 84f3669fbebe..819be757fa59 100644
--- a/lib/libarchive/archive_string.h
+++ b/lib/libarchive/archive_string.h
@@ -30,6 +30,9 @@
 #define	ARCHIVE_STRING_H_INCLUDED
 
 #include <stdarg.h>
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>  /* required for wchar_t on some systems */
+#endif
 #ifdef HAVE_STRING_H
 #include <string.h>
 #endif