diff --git a/ChangeLog b/ChangeLog
index 881c73ebea..e1bf3bc26a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Thu Dec 11 13:09:01 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* re.c (reg_enc_error): raise EncodingCompatibilityError for
+	  encoding incompatibility.  [ruby-core:18600]
+
+	* re.c (rb_reg_prepare_enc): more consistent error message.
+	  [ruby-core:18611]
+
 Thu Dec 11 13:36:18 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* encoding.c (enc_set_default_encoding): allowed to set default
diff --git a/re.c b/re.c
index a45ae47d9f..5ef1c7c49b 100644
--- a/re.c
+++ b/re.c
@@ -1168,7 +1168,7 @@ rb_reg_preprocess(const char *p, const char *end, rb_encoding *enc,
 static void
 reg_enc_error(VALUE re, VALUE str)
 {
-    rb_raise(rb_eArgError,
+    rb_raise(rb_eEncCompatError,
 	     "incompatible encoding regexp match (%s regexp with %s string)",
 	     rb_enc_name(RREGEXP(re)->ptr->enc),
 	     rb_enc_name(rb_enc_get(str)));
@@ -1181,7 +1181,7 @@ rb_reg_prepare_enc(VALUE re, VALUE str, int warn)
 
     if (rb_enc_str_coderange(str) == ENC_CODERANGE_BROKEN) {
         rb_raise(rb_eArgError,
-            "broken %s string",
+            "invalid byte sequence in %s",
             rb_enc_name(rb_enc_get(str)));
     }