diff --git a/testC14N.c b/testC14N.c
index dc1a9a6..f735a29 100644
--- a/testC14N.c
+++ b/testC14N.c
@@ -13,7 +13,9 @@
 #include <string.h>
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
-#endif
+#else
+#define STDOUT_FILENO fileno(stdout)
+#endif /* HAVE_UNISTD_H */
 #ifdef HAVE_STDLIB_H
 #include <stdlib.h>
 #endif