diff --git a/ChangeLog b/ChangeLog
index a271a0547c..c1141202c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Mon Apr 30 20:10:04 2012  Tanaka Akira  <akr@fsij.org>
+
+	* ext/zlib/extconf.rb: detect z_crc_t type which will be defined
+	  since zlib-1.2.7.
+
+	* ext/zlib/zlib.c (rb_zlib_crc_table): use z_crc_t if available.
+
 Mon Apr 30 09:02:15 2012  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
 
 	* ext/openssl/lib/openssl/ssl.rb: add hostname to "hostname does not
diff --git a/ext/zlib/extconf.rb b/ext/zlib/extconf.rb
index 499f55a046..d94fea743b 100644
--- a/ext/zlib/extconf.rb
+++ b/ext/zlib/extconf.rb
@@ -58,6 +58,7 @@ if %w'z libz zlib1 zlib zdll'.find {|z| have_library(z, 'deflateReset')} and
 
   have_func('crc32_combine', 'zlib.h')
   have_func('adler32_combine', 'zlib.h')
+  have_type('z_crc_t', 'zlib.h')
 
   create_makefile('zlib')
 
diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index d8cbe2fd65..fee74bfc98 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -505,7 +505,11 @@ rb_zlib_crc32_combine(VALUE klass, VALUE crc1, VALUE crc2, VALUE len2)
 static VALUE
 rb_zlib_crc_table(VALUE obj)
 {
-    const unsigned long *crctbl;
+#if !defined(HAVE_TYPE_Z_CRC_T)
+    /* z_crc_t is defined since zlib-1.2.7. */
+    typedef unsigned long z_crc_t;
+#endif
+    const z_crc_t *crctbl;
     VALUE dst;
     int i;