diff --git a/ChangeLog b/ChangeLog
index 520fcbdd4c..423dea433b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jul  9 20:58:16 2008  Tanaka Akira  <akr@fsij.org>
+
+	* array.c (rb_ary_fill): don't raise even if length is negative.
+	  [ruby-core:17483], [ruby-core:17661]
+
 Wed Jul  9 20:36:31 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* thread_{pthread,win32}.c (native_sleep): wait until timed out.
diff --git a/array.c b/array.c
index 646ea16526..2d5b5ace39 100644
--- a/array.c
+++ b/array.c
@@ -2141,10 +2141,12 @@ rb_ary_fill(int argc, VALUE *argv, VALUE ary)
 	    if (beg < 0) beg = 0;
 	}
 	len = NIL_P(arg2) ? RARRAY_LEN(ary) - beg : NUM2LONG(arg2);
-	if (len < 0) rb_raise(rb_eIndexError, "negative length (%ld)", len);
 	break;
     }
     rb_ary_modify(ary);
+    if (len < 0) {
+        return ary;
+    }
     if (beg >= ARY_MAX_SIZE || len > ARY_MAX_SIZE - beg) {
 	rb_raise(rb_eArgError, "argument too big");
     }