diff --git a/ChangeLog b/ChangeLog
index b7db9f8b12..09298022f5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Fri Dec 21 00:26:39 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* string.c (tr_trans): wrong encoding check for tree strings.
+
+	* test/ruby/test_m17n.rb (TestM17N::test_tr_s): "invalid mbstring
+	  sequence" is not an error to be tested.
+
 Thu Dec 20 19:29:07 2007  Shugo Maeda  <shugo@ruby-lang.org>
 
 	* lib/net/imap.rb (initialize): the second argument is an option
diff --git a/string.c b/string.c
index f1910af782..eecfc6347d 100644
--- a/string.c
+++ b/string.c
@@ -3453,7 +3453,7 @@ static VALUE
 tr_trans(VALUE str, VALUE src, VALUE repl, int sflag)
 {
     SIGNED_VALUE trans[256];
-    rb_encoding *enc;
+    rb_encoding *enc, *e1, *e2;
     struct tr trsrc, trrepl;
     int cflag = 0;
     int c, last = 0, modify = 0, i;
@@ -3471,9 +3471,13 @@ tr_trans(VALUE str, VALUE src, VALUE repl, int sflag)
     if (RSTRING_LEN(repl) == 0) {
 	return rb_str_delete_bang(1, &src, str);
     }
-    enc = rb_enc_check(str, src);
-    if (rb_enc_check(str, repl) != enc) {
-	rb_raise(rb_eArgError, "character encodings differ");
+    e1 = rb_enc_check(str, src);
+    e2 = rb_enc_check(str, repl);
+    if (e1 == e2) {
+	enc = e1;
+    }
+    else {
+	enc = rb_enc_check(src, repl);
     }
     trrepl.p = RSTRING_PTR(repl);
     trrepl.pend = trrepl.p + RSTRING_LEN(repl);
diff --git a/test/ruby/test_m17n.rb b/test/ruby/test_m17n.rb
index 8b06a2e07b..1923d9294e 100644
--- a/test/ruby/test_m17n.rb
+++ b/test/ruby/test_m17n.rb
@@ -1643,7 +1643,7 @@ class TestM17N < Test::Unit::TestCase
         #puts "#{encdump s1}.tr_s(#{encdump s2}, #{encdump s3})"
         t = s1.tr_s(s2, s3)
       rescue ArgumentError
-        e = $!
+        e = $! unless /mbstring sequence/ =~ $!.message
       end
       if e
         encs = []
@@ -1651,7 +1651,7 @@ class TestM17N < Test::Unit::TestCase
         encs << s2.encoding if !is_ascii_only?(s2)
         encs << s3.encoding if !is_ascii_only?(s3)
         encs.uniq!
-        #p e, encs
+        #p e, encs, 
         assert(1 < encs.length, "#{encdump s1}.tr_s(#{encdump s2}, #{encdump s3})")
       end
     }
diff --git a/version.h b/version.h
index ee0a9556fa..447c0416c4 100644
--- a/version.h
+++ b/version.h
@@ -1,7 +1,7 @@
 #define RUBY_VERSION "1.9.0"
-#define RUBY_RELEASE_DATE "2007-12-20"
+#define RUBY_RELEASE_DATE "2007-12-21"
 #define RUBY_VERSION_CODE 190
-#define RUBY_RELEASE_CODE 20071220
+#define RUBY_RELEASE_CODE 20071221
 #define RUBY_PATCHLEVEL 0
 
 #define RUBY_VERSION_MAJOR 1
@@ -9,7 +9,7 @@
 #define RUBY_VERSION_TEENY 0
 #define RUBY_RELEASE_YEAR 2007
 #define RUBY_RELEASE_MONTH 12
-#define RUBY_RELEASE_DAY 20
+#define RUBY_RELEASE_DAY 21
 
 #ifdef RUBY_EXTERN
 RUBY_EXTERN const char ruby_version[];