diff --git a/src/fmt/time.c b/src/fmt/time.c
index ecf5873f6..76410c438 100644
--- a/src/fmt/time.c
+++ b/src/fmt/time.c
@@ -5,7 +5,7 @@
  */
 
 #ifdef __MINGW32__
-#define _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200809L
 #endif
 
 #include <time.h>