diff --git a/ChangeLog b/ChangeLog
index b0b263c200..dfdef8a91c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Jan 10 12:57:12 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
+
+	* ext/zlib/zlib.c: fix document of method signatures.
+	  [Bug #10668][ruby-core:67186][ci skip]
+
 Sat Jan 10 12:32:44 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* eval_error.c (error_print): pos and len parameters of rb_str_substr()
diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index cfdc9a50f7..8f24b77d8f 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -465,7 +465,7 @@ rb_zlib_adler32_combine(VALUE klass, VALUE adler1, VALUE adler2, VALUE len2)
 /*
  * Document-method: Zlib.crc32
  *
- * call-seq: Zlib.crc32(string, adler)
+ * call-seq: Zlib.crc32(string, crc)
  *
  * Calculates CRC checksum for +string+, and returns updated value of +crc+. If
  * +string+ is omitted, it returns the CRC initial value. If +crc+ is omitted, it