diff --git a/src/fmacros.h b/src/fmacros.h
index 38f46482..866a9afa 100644
--- a/src/fmacros.h
+++ b/src/fmacros.h
@@ -3,7 +3,7 @@
 
 #define _BSD_SOURCE
 
-#ifdef __linux__
+#if defined(__linux__) || defined(__OpenBSD__)
 #define _XOPEN_SOURCE 700
 #else
 #define _XOPEN_SOURCE