diff --git a/ChangeLog b/ChangeLog
index 9cb4803f2f..818288ccf8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed May 20 21:00:27 2009  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
+
+	* rb_enc_get_index: allows an arbitrary RData as the argument but not
+	  only what points a rb_encoding.
+
 Wed May 20 20:54:37 2009  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
 
 	* spec/.gitignore: ignores rubyspec/ and mspec/.
diff --git a/encoding.c b/encoding.c
index 4ef45cd65e..574193a96f 100644
--- a/encoding.c
+++ b/encoding.c
@@ -566,6 +566,7 @@ rb_enc_get_index(VALUE obj)
     VALUE tmp;
 
     switch (BUILTIN_TYPE(obj)) {
+as_default:
         default:
 	case T_STRING:
 	case T_REGEXP:
@@ -586,6 +587,9 @@ rb_enc_get_index(VALUE obj)
 	    if (RDATA(obj)->dmark == enc_mark) {
 		i = enc_check_encoding(obj);
 	    }
+            else {
+                goto as_default;
+            }
 	    break;
     }
     return i;