diff --git a/ChangeLog b/ChangeLog
index cb74880586..370e924a9f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun May 30 02:21:34 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* ext/zlib/zlib.c (zstream_append_input2): add RB_GC_GUARD.
+	  This caused failure when test/csv is executed with GC.stress = true.
+
 Sun May 30 01:25:48 2010  Masaya Tarui  <tarui@ruby-lnag.org>
 
 	* thread.c (RB_GC_SAVE_MACHINE_CONTEXT): start GC 
diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index f4abe43469..452f91acf2 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -661,6 +661,7 @@ zstream_append_input(struct zstream *z, const Bytef *src, unsigned int len)
 }
 
 #define zstream_append_input2(z,v)\
+    RB_GC_GUARD(v),\
     zstream_append_input((z), (Bytef*)RSTRING_PTR(v), RSTRING_LEN(v))
 
 static void