diff --git a/src/fmacros.h b/src/fmacros.h
index e49735ce..6e56c759 100644
--- a/src/fmacros.h
+++ b/src/fmacros.h
@@ -34,6 +34,7 @@
 
 #if defined(__linux__)
 #define _GNU_SOURCE
+#define _DEFAULT_SOURCE
 #endif
 
 #if defined(_AIX)