diff --git a/src/dfa.jl b/src/dfa.jl
index 69f52ac2..fadb58f2 100644
--- a/src/dfa.jl
+++ b/src/dfa.jl
@@ -21,11 +21,11 @@ function nfa2dfa(nfa::NFA)
     S = epsilon_closure(Set([nfa.start]))
     start = new_dfanode(S)
     dfanodes = Dict([S => start])
-    unvisited = Set([S])
+    unvisited = [S]
     while !isempty(unvisited)
         S = pop!(unvisited)
         S_actions = accumulate_actions(S)
-        for l in 0x00:0xff
+        for l in keyrange(S)
             T = epsilon_closure(move(S, l))
             if isempty(T)
                 continue
@@ -35,6 +35,9 @@ function nfa2dfa(nfa::NFA)
             end
             actions = Set{Action}()
             for s in S
+                if !haskey(s.trans, l)
+                    continue
+                end
                 T′ = s.trans[l]
                 for t in T′
                     union!(actions, s.actions[(l, t)])
@@ -52,17 +55,31 @@ function nfa2dfa(nfa::NFA)
     return DFA(start)
 end
 
+function keyrange(S::Set{NFANode})
+    lo = 0xff
+    hi = 0x00
+    for s in S
+        for l in bytekeys(s.trans)
+            lo = min(l, lo)
+            hi = max(l, hi)
+        end
+    end
+    return lo:hi
+end
+
 function move(S::Set{NFANode}, label::UInt8)
     T = Set{NFANode}()
     for s in S
-        union!(T, s.trans[label])
+        if haskey(s.trans, label)
+            union!(T, s.trans[label])
+        end
     end
     return T
 end
 
 function epsilon_closure(S::Set{NFANode})
     closure = Set{NFANode}()
-    unvisited = Set(copy(S))
+    unvisited = collect(S)
     while !isempty(unvisited)
         s = pop!(unvisited)
         push!(closure, s)
@@ -105,7 +122,7 @@ function reduce_states(dfa::DFA)
     new_dfanode(s) = DFANode(Dict(), Set{Action}(), s.final, Set{NFANode}())
     start = new_dfanode(dfa.start)
     S_start = equivalent(dfa.start)
-    dfanodes = Dict([S_start => start])
+    dfanodes = Dict(S_start => start)
     unvisited = [(S_start, start)]
     while !isempty(unvisited)
         S, s′ = pop!(unvisited)
diff --git a/src/nfa.jl b/src/nfa.jl
index 1f920ebe..2753b8a8 100644
--- a/src/nfa.jl
+++ b/src/nfa.jl
@@ -39,6 +39,14 @@ function NFATransition()
     return NFATransition(trans, trans_eps)
 end
 
+function bytekeys(trans::NFATransition)
+    return keys(trans.trans)
+end
+
+function Base.haskey(trans::NFATransition, label::UInt8)
+    return haskey(trans.trans, label)
+end
+
 function Base.getindex(trans::NFATransition, label::UInt8)
     return trans.trans[label]
 end
@@ -154,6 +162,18 @@ function re2nfa_rec(re::RegExp.RE, actions::Dict{Symbol,Action})
         for b in re.args[1]
             addtrans!(start, b => final)
         end
+    elseif re.head == :bytes
+        if isempty(re.args)
+            addtrans!(start, :eps => final)
+        else
+            node = start
+            for b::UInt8 in re.args
+                next = NFANode()
+                addtrans!(node, b => next)
+                node = next
+            end
+            final = node
+        end
     elseif re.head == :cat
         lastnfa = NFA(start, final)
         addtrans!(start, :eps => final)
diff --git a/src/re.jl b/src/re.jl
index 111f9c95..5481e24d 100644
--- a/src/re.jl
+++ b/src/re.jl
@@ -50,7 +50,7 @@ function primitive(str::String)
 end
 
 function primitive(bs::Vector{UInt8})
-    return RE(:bytes, [bs])
+    return RE(:bytes, copy(bs))
 end
 
 function primitive(x::Primitive, actions)
@@ -325,9 +325,9 @@ function expand(re::RE)
             return expand(primitive(string(char), re.actions))
         end
     elseif re.head == :str
-        return expand(primitive(convert(Vector{UInt8}, re.args[1]), re.actions))
+        return RE(:bytes, convert(Vector{UInt8}, re.args[1]), re.actions)
     elseif re.head == :bytes
-        return RE(:cat, [primitive(ByteSet([b])) for b in re.args[1]], re.actions)
+        return re
     else
         @assert re.head ∉ PRIMITIVE
         return RE(re.head, [expand(arg) for arg in re.args], re.actions)