diff --git a/ChangeLog b/ChangeLog
index ea2a7b53de..16199aa465 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Dec 15 01:33:31 2005  Tanaka Akira  <akr@m17n.org>
+
+	* ext/zlib/zlib.c (zstream_run): fix a GC problem by tail call on
+	  x86_64 with gcc 4.0.3 20051111 (prerelease) (Debian 4.0.2-4)
+
 Wed Dec 14 23:50:20 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/rdoc/parsers/parse_c.rb (find_class_comment): fix for class
diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index b05e5264c5..923e3a72bb 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -762,6 +762,7 @@ zstream_run(z, src, len, flush)
     zstream_reset_input(z);
     if (z->stream.avail_in > 0) {
 	zstream_append_input(z, z->stream.next_in, z->stream.avail_in);
+        guard = Qnil; /* prevent tail call to make guard effective */
     }
 }