diff --git a/src/utils.c b/src/utils.c
index a910cfb96..e11bc09d5 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -1,4 +1,5 @@
 #ifndef _WIN32
+#  define _POSIX_C_SOURCE 200809L // required for POSIX (not standard C) features in is_direct_child e.g. 'siginfo_t'
 #  include <sys/wait.h>
 #endif