diff --git a/gl/unistd.in.h b/gl/unistd.in.h
index 2ea9af4..ed58960 100644
--- a/gl/unistd.in.h
+++ b/gl/unistd.in.h
@@ -116,6 +116,7 @@
 # include <getopt.h>
 #endif
 
+#include "config.h"
 _GL_INLINE_HEADER_BEGIN
 #ifndef _GL_UNISTD_INLINE
 # define _GL_UNISTD_INLINE _GL_INLINE