diff --git a/src/c/util/core/stest.c b/src/c/util/core/stest.c
index 42edc226..7f6c674c 100644
--- a/src/c/util/core/stest.c
+++ b/src/c/util/core/stest.c
@@ -15,6 +15,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L
+#define _XOPEN_SOURCE 600
 
 #include <dirent.h>
 #include <errno.h>