diff --git a/ext/dl/lib/dl/types.rb b/ext/dl/lib/dl/types.rb
index 6fc373b797..139426473a 100644
--- a/ext/dl/lib/dl/types.rb
+++ b/ext/dl/lib/dl/types.rb
@@ -53,7 +53,7 @@ module DL
 	proc{|v| (v != 0) ? true : false},
 	proc{|v,len| v ? 1 : 0},
 	proc{|v,len| (v != 0) ? true : false}],
-      ["unsigned char", "I",
+      ["unsigned char", "C",
 	proc{|v| [v].pack("C").unpack("c")[0]},
 	proc{|v| [v].pack("c").unpack("C")[0]},
 	proc{|v| [v].pack("C").unpack("c")[0]},
@@ -73,7 +73,7 @@ module DL
 	proc{|v| [v].pack("l").unpack("L")[0]},
 	proc{|v| [v].pack("L").unpack("l")[0]},
 	proc{|v| [v].pack("l").unpack("L")[0]}],
-      ["unsigned char ref", "i",
+      ["unsigned char ref", "c",
 	proc{|v| [v].pack("C").unpack("c")[0]},
 	proc{|v| [v].pack("c").unpack("C")[0]},
 	nil, nil],