diff --git a/src/ast.jl b/src/ast.jl
index ecc40b0..a4aa04e 100644
--- a/src/ast.jl
+++ b/src/ast.jl
@@ -62,7 +62,7 @@ end
 # Close to single assignment form
 mutable struct FlatAST
     top  # topmost variable(s)
-    input_variables::Set{Symbol}
+    input_variables::Vector{Symbol}
     intermediate::Vector{Symbol}  # generated vars
     code # ::Vector{Assignment}
     variables::Vector{Symbol}  # cleaned version of input_variables
@@ -76,7 +76,7 @@ function Base.show(io::IO, flatAST::FlatAST)
     println(io, "code: ", flatAST.code)
 end
 
-FlatAST() = FlatAST([], Set{Symbol}(), [], [], [])
+FlatAST() = FlatAST([], [], [], [], [])
 
 export FlatAST
 
diff --git a/src/code_generation.jl b/src/code_generation.jl
index fb50f55..d2d239c 100644
--- a/src/code_generation.jl
+++ b/src/code_generation.jl
@@ -133,9 +133,7 @@ function forward_backward(flatAST::FlatAST)
 
     # @show flatAST.input_variables
     # @show flatAST.intermediate
-
-
-    input = sort(collect(flatAST.input_variables))
+    input = collect(flatAST.input_variables)
 
     # @show flatAST.top
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 230c836..0e000b4 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -65,6 +65,11 @@ end
     C2 = Contractor([x, y, z], y+z)
     @test C2(A,X) == IntervalBox(0.5..1.5, 0.5..0.5, 0.5..0.5)
 
+    vars = @variables x1 x3 x2
+
+    C = Contractor(vars, x1+x2)
+    @test C(A, X) == IntervalBox(0.5..0.5, 0.5..1.5, 0.5..0.5)
+
 end
 
 @testset "Contractor is created by function name " begin