diff -u djbfft-0.76.orig/error.h djbfft-0.76/error.h
--- djbfft-0.76.orig/error.h	2014-07-20 12:25:48.000000000 -0600
+++ djbfft-0.76/error.h	2016-07-01 13:37:59.303921704 -0600
@@ -1,7 +1,7 @@
 #ifndef ERROR_H
 #define ERROR_H
 
-extern int errno;
+#include <errno.h>
 
 extern int error_intr;
 extern int error_nomem;