diff --git a/config-unix.mk b/config-unix.mk
index 2b44dd64..13526827 100644
--- a/config-unix.mk
+++ b/config-unix.mk
@@ -65,6 +65,8 @@ endif
 ifneq (,$(findstring CYGWIN,$(uname_S)))
 EV_CONFIG=config_cygwin.h
 EIO_CONFIG=config_cygwin.h
+# We drop the --std=c89, it hides CLOCK_MONOTONIC on cygwin
+CSTDFLAG = -D_GNU_SOURCE
 CPPFLAGS += -Isrc/ares/config_cygwin
 LINKFLAGS+=
 UV_OS_FILE=uv-cygwin.c
diff --git a/src/uv-unix.c b/src/uv-unix.c
index 35443922..842fe326 100644
--- a/src/uv-unix.c
+++ b/src/uv-unix.c
@@ -18,7 +18,9 @@
  * IN THE SOFTWARE.
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE /* O_CLOEXEC, accept4(), etc. */
+#endif
 
 #include "uv.h"
 #include "uv-common.h"