diff --git a/gzip.jl b/gzip.jl
index b2cdc93..55777c8 100644
--- a/gzip.jl
+++ b/gzip.jl
@@ -4,7 +4,7 @@ type BitStream
 end
 BitStream(io::IO) = BitStream(io, BitVector(0))
 
-typealias GzipFlags UInt8
+const GzipFlags = UInt8
 
 type GzipHeader
   id::Vector{UInt8} # length 2
@@ -166,7 +166,7 @@ function make_bit_vector(n::Any, len::Any)
 end
 #read_huffman_stream(file)
 
-abstract Node
+abstract type Node end
 
 type InternalNode <: Node
     one::Node
@@ -226,7 +226,7 @@ function read_first_tree(bs::BitStream, hclen)
     return first_tree
 end
 
-typealias HuffmanTree InternalNode
+const HuffmanTree = InternalNode
 
 function read_huffman_bits(bs::BitStream, tree::HuffmanTree)
     node = tree