diff --git a/ChangeLog b/ChangeLog
index fc78dd4680..e0da0e0336 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Oct  1 23:08:47 2016  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/date/date_parse.c (date_zone_to_diff): it's nonsence and really
+	  harm that to use unary minus operator with unsigned value.
+	  get rid of test failures introduced at r56312.
+
 Sat Oct  1 22:17:49 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* compile.c (iseq_compile_each): move numeric literal range
diff --git a/ext/date/date_parse.c b/ext/date/date_parse.c
index 97923d7623..b74230d291 100644
--- a/ext/date/date_parse.c
+++ b/ext/date/date_parse.c
@@ -415,7 +415,7 @@ date_zone_to_diff(VALUE str)
 	{
 	    char *p;
 	    int sign = 0;
-	    unsigned long hour = 0, min = 0, sec = 0;
+	    long hour = 0, min = 0, sec = 0;
 
 	    if (l > 3 &&
 		(strncmp(s, "gmt", 3) == 0 ||