diff --git a/ChangeLog b/ChangeLog
index 5db122c023..642dce5bda 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Oct 17 21:49:52 2014  Tanaka Akira  <akr@fsij.org>
+
+	* pack.c (pack_unpack): Add casts for char references for 'b' and 'h'.
+
 Fri Oct 17 17:50:10 2014  Tanaka Akira  <akr@fsij.org>
 
 	* Avoid undefined behaviors found by gcc -fsanitize=undefined.
diff --git a/pack.c b/pack.c
index d9283b7ea6..0cf2dc37b7 100644
--- a/pack.c
+++ b/pack.c
@@ -1343,7 +1343,7 @@ pack_unpack(VALUE str, VALUE fmt)
 		t = RSTRING_PTR(bitstr);
 		for (i=0; i<len; i++) {
 		    if (i & 7) bits >>= 1;
-		    else bits = *s++;
+		    else bits = (unsigned char)*s++;
 		    *t++ = (bits & 1) ? '1' : '0';
 		}
 	    }
@@ -1385,7 +1385,7 @@ pack_unpack(VALUE str, VALUE fmt)
 		    if (i & 1)
 			bits >>= 4;
 		    else
-			bits = *s++;
+			bits = (unsigned char)*s++;
 		    *t++ = hexdigits[bits & 15];
 		}
 	    }