diff --git a/lib/bit-struct/unsigned-field.rb b/lib/bit-struct/unsigned-field.rb
index 34be578598..3b79c52f0b 100644
--- a/lib/bit-struct/unsigned-field.rb
+++ b/lib/bit-struct/unsigned-field.rb
@@ -39,8 +39,8 @@ class BitStruct
       
       if length_byte == 1
         rest = 8 - length_bit
-        mask  = ["0"*offset_bit + "1"*length + "0"*rest].pack("B8")[0].ord
-        mask2 = ["1"*offset_bit + "0"*length + "1"*rest].pack("B8")[0].ord
+        mask  = ["0"*offset_bit + "1"*length + "0"*rest].pack("B8")[0,1].unpack('C')[0]
+        mask2 = ["1"*offset_bit + "0"*length + "1"*rest].pack("B8")[0,1].unpack('C')[0]
         
         cl.class_eval do
           if divisor