diff --git a/lib/str.h b/lib/str.h
index cffa03ffa..b6ac597b6 100644
--- a/lib/str.h
+++ b/lib/str.h
@@ -7,6 +7,7 @@
 #include <stdarg.h>
 #include <assert.h>
 #include <stdio.h>
+#include <errno.h>
 #include "compat.h"
 #include "containers.h"