diff --git a/ChangeLog b/ChangeLog
index 373e601709..54d8870b65 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jun  9 23:35:22 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* enum.c (enum_inject): default the result value to Qundef to use
+	  first element as initial value if not given.
+
 Thu Jun  9 19:55:41 2005  Tanaka Akira  <akr@m17n.org>
 
 	* eval.c (ruby_longjmp): new macro to call longjmp, setcontext, etc.
diff --git a/enum.c b/enum.c
index 00d7a58a7e..25432dc99a 100644
--- a/enum.c
+++ b/enum.c
@@ -305,8 +305,10 @@ enum_inject(argc, argv, obj)
 {
     VALUE memo = Qundef;
 
-    rb_scan_args(argc, argv, "01", &memo);
+    if (rb_scan_args(argc, argv, "01", &memo) == 0)
+	memo = Qundef;
     rb_iterate(rb_each, obj, inject_i, (VALUE)&memo);
+    if (memo == Qundef) return Qnil;
     return memo;
 }