diff --git a/src/haproxy.c b/src/haproxy.c
index f12e903b2..bcbbad4a1 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2631,6 +2631,13 @@ int main(int argc, char **argv)
 			}
 		}
 
+		/* if in master-worker mode, write the PID of the father */
+		if (global.mode & MODE_MWORKER) {
+			char pidstr[100];
+			snprintf(pidstr, sizeof(pidstr), "%d\n", getpid());
+			shut_your_big_mouth_gcc(write(pidfd, pidstr, strlen(pidstr)));
+		}
+
 		/* the father launches the required number of processes */
 		for (proc = 0; proc < global.nbproc; proc++) {
 			ret = fork();