1 files changed, 1 insertions, 1 deletions
diff --git a/process.c b/process.c
index bdf651f37b..1ed5dd935a 100644
--- a/process.c
+++ b/process.c
@@ -1267,7 +1267,7 @@ rb_f_exec(argc, argv)
     else {
 	e.argc = argc;
 	e.argv = argv;
-	e.prog = RSTRING(prog)->ptr;
+	e.prog = prog ? RSTRING(prog)->ptr : 0;
     }
     rb_exec(&e);
     rb_sys_fail(e.prog);