diff --git a/ChangeLog b/ChangeLog
index cc40716066..747c97de7d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jan 24 21:46:24 2008  Tanaka Akira  <akr@fsij.org>
+
+	* parse.y (reg_fragment_setenc_gen): associate ASCII-8BIT only if
+	  str has only ASCII characters.
+
 Thu Jan 24 20:46:17 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* test/ruby/test_m17n.rb: follow to the following changes.
diff --git a/parse.y b/parse.y
index b43dc64b70..140e320fea 100644
--- a/parse.y
+++ b/parse.y
@@ -8475,17 +8475,26 @@ reg_fragment_setenc_gen(struct parser_params* parser, VALUE str, int options)
     if (c) {
 	int opt, idx;
 	rb_char_to_option_kcode(c, &opt, &idx);
-	if (idx != ENCODING_GET(str) && !ENCODING_IS_ASCII8BIT(str) &&
+	if (idx != ENCODING_GET(str) &&
 	    rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT) {
-	    compile_error(PARSER_ARG
-			  "regexp encoding option '%c' differs from source encoding '%s'",
-			  c, rb_enc_name(rb_enc_get(str)));
+            goto error;
 	}
 	ENCODING_SET(str, idx);
     }
     else if (RE_OPTION_ENCODING_NONE(options)) {
+        if (!ENCODING_IS_ASCII8BIT(str) &&
+            rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT) {
+            c = 'n';
+            goto error;
+        }
 	rb_enc_associate(str, rb_ascii8bit_encoding());
     }
+    return;
+
+error:
+    compile_error(PARSER_ARG
+        "regexp encoding option '%c' differs from source encoding '%s'",
+        c, rb_enc_name(rb_enc_get(str)));
 }
 
 static void