diff --git a/lib/full-write.c b/lib/full-write.c
index 339fb1a48..2a65ac5e5 100644
--- a/lib/full-write.c
+++ b/lib/full-write.c
@@ -29,7 +29,7 @@
 #endif
 
 #include <errno.h>
-#ifndef STDC_HEADERS
+#ifndef errno
 extern int errno;
 #endif