diff --git a/ChangeLog b/ChangeLog
index 9134621c74..ca67590b32 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Aug 29 18:20:56 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* string.c (rb_str_index_m): only regexp uses byte offset.
+
+	* string.c (rb_str_rindex_m): ditto.
+
 Fri Aug 29 16:48:34 2008  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_insnhelper.c (vm_call_method): copy arguments to allocated
diff --git a/string.c b/string.c
index 180d869acd..f835f5e7d1 100644
--- a/string.c
+++ b/string.c
@@ -2167,11 +2167,11 @@ rb_str_index_m(int argc, VALUE *argv, VALUE str)
 	}
     }
 
-    pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
-	    rb_enc_check(str, sub), single_byte_optimizable(str));
-
     switch (TYPE(sub)) {
       case T_REGEXP:
+	pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
+		     rb_enc_check(str, sub), single_byte_optimizable(str));
+
 	pos = rb_reg_adjust_startpos(sub, str, pos, 0);
 	pos = rb_reg_search(sub, str, pos, 0);
 	pos = rb_str_sublen(str, pos);
@@ -2280,12 +2280,12 @@ rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
 	pos = len;
     }
 
-    pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
-	    rb_enc_check(str, sub), single_byte_optimizable(str));
-
     switch (TYPE(sub)) {
       case T_REGEXP:
 	/* enc = rb_get_check(str, sub); */
+	pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
+		     rb_enc_check(str, sub), single_byte_optimizable(str));
+
 	if (!RREGEXP(sub)->ptr || RREGEXP_SRC_LEN(sub)) {
 	    pos = rb_reg_adjust_startpos(sub, str, pos, 1);
 	    pos = rb_reg_search(sub, str, pos, 1);