diff --git a/ChangeLog b/ChangeLog
index f901ab7904..4a210a0825 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Dec 17 11:01:35 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_hash): gets rid of collisions between differen
+	  encoding strings.  [ruby-core:20526]
+
 Wed Dec 17 09:50:19 2008  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
 
 	* test/ruby/test_metaclass.rb: removed codes for my debugging.
diff --git a/string.c b/string.c
index f940966753..d34a1e861c 100644
--- a/string.c
+++ b/string.c
@@ -2014,7 +2014,11 @@ rb_memhash(const void *ptr, long len)
 int
 rb_str_hash(VALUE str)
 {
-    return rb_memhash((const void *)RSTRING_PTR(str), RSTRING_LEN(str));
+    int e = ENCODING_GET(str);
+    if (e) {
+	if (rb_enc_str_asciionly_p(str)) e = 0;
+    }
+    return rb_memhash((const void *)RSTRING_PTR(str), RSTRING_LEN(str)) ^ e;
 }
 
 int