diff --git a/ChangeLog b/ChangeLog
index dd3cbfe800..30d80a78ae 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Dec 24 18:37:32 2007  Tanaka Akira  <akr@fsij.org>
+
+	* re.c (rb_reg_prepare_re): show regexp encoding in the error message.
+
 Mon Dec 24 18:23:32 2007  Tanaka Akira  <akr@fsij.org>
 
 	* eval.c (rb_exc_raise): ANSI style.
diff --git a/re.c b/re.c
index f6e4c76761..dcbc234602 100644
--- a/re.c
+++ b/re.c
@@ -945,7 +945,10 @@ rb_reg_prepare_re(VALUE re, VALUE str)
     if (rb_reg_fixed_encoding_p(re)) {
         if (ENCODING_GET(re) != rb_enc_get_index(str) &&
             rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT) {
-            rb_raise(rb_eArgError, "fixed character encoding regexp with incompatible string (encoding: %s)", rb_enc_name(rb_enc_get(str)));
+            rb_raise(rb_eArgError,
+                "incompatible encoding regexp match (%s regexp with %s string)",
+                rb_enc_name(rb_enc_from_index(ENCODING_GET(re))),
+                rb_enc_name(rb_enc_get(str)));
         }
     }
     else {