diff --git a/die-with-parent.c b/die-with-parent.c
index c005923..150e63c 100644
--- a/die-with-parent.c
+++ b/die-with-parent.c
@@ -14,7 +14,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#define PID_MAX ((((size_t) 1) << (sizeof(pid_t) * 8)) + 1)
+#define PID_MAX ((((size_t) 1) << (sizeof(pid_t) * 8)) - 1)
 
 static const char *EXEC_NAME;