diff --git a/wrappers/Julia/CoolProp.jl b/wrappers/Julia/CoolProp.jl
index 0a29e91c..2f5cf7a2 100644
--- a/wrappers/Julia/CoolProp.jl
+++ b/wrappers/Julia/CoolProp.jl
@@ -8,6 +8,7 @@ if VERSION <= VersionNumber(0,4)
   typealias Ref Ptr
   typealias RefValue Array
   errcode = Array(Clong, 1)
+  typealias AbstractString String
 else
   errcode = Ref{Clong}(0)
 end
@@ -23,7 +24,7 @@ function K2F(TK::Number)
   return ccall( (:K2F, "CoolProp"), Cdouble, (Cdouble,), TK)
 end
 
-function HAPropsSI(Output::String, Name1::String, Value1::Number, Name2::String, Value2::Number, Name3::String, Value3::Number)
+function HAPropsSI(Output::AbstractString, Name1::AbstractString, Value1::Number, Name2::AbstractString, Value2::Number, Name3::AbstractString, Value3::Number)
   val = ccall( (:HAPropsSI, "CoolProp"), Cdouble, (Ptr{UInt8},Ptr{UInt8},Float64,Ptr{UInt8},Float64,Ptr{UInt8},Float64), Output,Name1,Value1,Name2,Value2,Name3,Value3)
   if val == Inf
     error("CoolProp: ", get_global_param_string("errstring"))
@@ -31,7 +32,7 @@ function HAPropsSI(Output::String, Name1::String, Value1::Number, Name2::String,
   return val
 end
 
-function PropsSI(Output::String, Name1::String, Value1::Number, Name2::String, Value2::Number, Fluid::String)
+function PropsSI(Output::AbstractString, Name1::AbstractString, Value1::Number, Name2::AbstractString, Value2::Number, Fluid::AbstractString)
   val = ccall( (:PropsSI, "CoolProp"), Cdouble, (Ptr{UInt8},Ptr{UInt8},Float64,Ptr{UInt8},Float64,Ptr{UInt8}), Output,Name1,Value1,Name2,Value2,Fluid)
   if val == Inf
     error("CoolProp: ", get_global_param_string("errstring"))
@@ -39,7 +40,7 @@ function PropsSI(Output::String, Name1::String, Value1::Number, Name2::String, V
   return val
 end
 
-function PropsSI(FluidName::String, Output::String)
+function PropsSI(FluidName::AbstractString, Output::AbstractString)
   val = ccall( (:Props1SI, "CoolProp"), Cdouble, (Ptr{UInt8},Ptr{UInt8}), FluidName,Output)
   if val == Inf
     error("CoolProp: ", get_global_param_string("errstring"))
@@ -47,20 +48,20 @@ function PropsSI(FluidName::String, Output::String)
   return val
 end
 
-function PhaseSI(Name1::String, Value1::Number, Name2::String, Value2::Number, Fluid::String)
-  val = ccall( (:PhaseSI, "CoolProp"), Int32, (Ptr{UInt8},Float64,Ptr{UInt8},Float64,Ptr{UInt8}, Ptr{UInt8}, Int), Name1,Value1,Name2,Value2,Fluid,message_buffer::Array{Uint8,1},buffer_length)
-  return bytestring(convert(Ptr{UInt8}, pointer(message_buffer::Array{Uint8,1})))
+function PhaseSI(Name1::AbstractString, Value1::Number, Name2::AbstractString, Value2::Number, Fluid::AbstractString)
+  val = ccall( (:PhaseSI, "CoolProp"), Int32, (Ptr{UInt8},Float64,Ptr{UInt8},Float64,Ptr{UInt8}, Ptr{UInt8}, Int), Name1,Value1,Name2,Value2,Fluid,message_buffer::Array{UInt8,1},buffer_length)
+  return bytestring(convert(Ptr{UInt8}, pointer(message_buffer::Array{UInt8,1})))
 end
 
 # This function returns the output string in pre-allocated char buffer.  If buffer is not large enough, no copy is made
-function get_global_param_string(Key::String)
-  val = ccall( (:get_global_param_string, "CoolProp"), Clong, (Ptr{UInt8},Ptr{UInt8},Int), Key,message_buffer::Array{Uint8,1},buffer_length)
-  return bytestring(convert(Ptr{UInt8}, pointer(message_buffer::Array{Uint8,1})))
+function get_global_param_string(Key::AbstractString)
+  val = ccall( (:get_global_param_string, "CoolProp"), Clong, (Ptr{UInt8},Ptr{UInt8},Int), Key,message_buffer::Array{UInt8,1},buffer_length)
+  return bytestring(convert(Ptr{UInt8}, pointer(message_buffer::Array{UInt8,1})))
 end
 
 # Get the index for a parameter "T", "P", etc.
 # returns the index as a long.
-function get_param_index(Param::String)
+function get_param_index(Param::AbstractString)
   val = ccall( (:get_param_index, "CoolProp"), Clong, (Ptr{UInt8},), Param)
   if val == -1
     error("CoolProp: Unknown parameter: ", Param)
@@ -70,7 +71,7 @@ end
 
 # Get the index for an input pair for AbstractState.update function
 # returns the index as a long.
-function get_input_pair_index(Param::String)
+function get_input_pair_index(Param::AbstractString)
   val = ccall( (:get_input_pair_index, "CoolProp"), Clong, (Ptr{UInt8},), Param)
   if val == -1
     error("CoolProp: Unknown input pair: ", Param)
@@ -98,8 +99,8 @@ end
 # param backend The backend you will use, "HEOS", "REFPROP", etc.
 # param fluids '&' delimited list of fluids
 # return A handle to the state class generated
-function AbstractState_factory(backend::String, fluids::String)
-  AbstractState = ccall( (:AbstractState_factory, "CoolProp"), Clong, (Ptr{UInt8},Ptr{UInt8},Ref{Clong},Ptr{UInt8},Clong), backend,fluids,errcode::RefValue{Clong,1},message_buffer::Array{Uint8,1},buffer_length)
+function AbstractState_factory(backend::AbstractString, fluids::AbstractString)
+  AbstractState = ccall( (:AbstractState_factory, "CoolProp"), Clong, (Ptr{UInt8},Ptr{UInt8},Ref{Clong},Ptr{UInt8},Clong), backend,fluids,errcode::RefValue{Clong,1},message_buffer::Array{UInt8,1},buffer_length)
   if errcode[] != 0
     if errcode[] == 1
       error("CoolProp: ", bytestring(convert(Ptr{UInt8}, pointer(message_buffer))))
@@ -115,7 +116,7 @@ end
 # Release a state class generated by the low-level interface wrapper
 # param handle The integer handle for the state class stored in memory
 function AbstractState_free(handle::Clong)
-  ccall( (:AbstractState_free, "CoolProp"), Void, (Clong,Ref{Clong},Ptr{UInt8},Clong), handle,errcode::RefValue{Clong,1},message_buffer::Array{Uint8,1},buffer_length)
+  ccall( (:AbstractState_free, "CoolProp"), Void, (Clong,Ref{Clong},Ptr{UInt8},Clong), handle,errcode::RefValue{Clong,1},message_buffer::Array{UInt8,1},buffer_length)
   if errcode[] != 0
     if errcode[] == 1
       error("CoolProp: ", bytestring(convert(Ptr{UInt8}, pointer(message_buffer))))
@@ -132,7 +133,7 @@ end
 # param handle The integer handle for the state class stored in memory
 # param fractions The array of fractions
 function AbstractState_set_fractions(handle::Clong,fractions::Array)
-  ccall( (:AbstractState_set_fractions, "CoolProp"), Void, (Clong,Ptr{Cdouble},Clong,Ref{Clong},Ptr{UInt8},Clong), handle,fractions,length(fractions),errcode::RefValue{Clong,1},message_buffer::Array{Uint8,1},buffer_length)
+  ccall( (:AbstractState_set_fractions, "CoolProp"), Void, (Clong,Ptr{Cdouble},Clong,Ref{Clong},Ptr{UInt8},Clong), handle,fractions,length(fractions),errcode::RefValue{Clong,1},message_buffer::Array{UInt8,1},buffer_length)
   if errcode[] != 0
     if errcode[] == 1
       error("CoolProp: ", bytestring(convert(Ptr{UInt8}, pointer(message_buffer))))
@@ -147,11 +148,11 @@ end
 
 # Update the state of the AbstractState
 # param handle The integer handle for the state class stored in memory
-# param input_pair The integer value for the input pair obtained from get_input_pair_index(Param::String)
+# param input_pair The integer value for the input pair obtained from get_input_pair_index(Param::AbstractString)
 # param value1 The first input value
 # param value2 The second input value
 function AbstractState_update(handle::Clong,input_pair::Clong,value1::Number,value2::Number)
-  ccall( (:AbstractState_update, "CoolProp"), Void, (Clong,Clong,Cdouble,Cdouble,Ref{Clong},Ptr{UInt8},Clong), handle,input_pair,value1,value2,errcode::RefValue{Clong,1},message_buffer::Array{Uint8,1},buffer_length)
+  ccall( (:AbstractState_update, "CoolProp"), Void, (Clong,Clong,Cdouble,Cdouble,Ref{Clong},Ptr{UInt8},Clong), handle,input_pair,value1,value2,errcode::RefValue{Clong,1},message_buffer::Array{UInt8,1},buffer_length)
   if errcode[] != 0
     if errcode[] == 1
       error("CoolProp: ", bytestring(convert(Ptr{UInt8}, pointer(message_buffer))))
@@ -168,7 +169,7 @@ end
 # param handle The integer handle for the state class stored in memory
 # param param The integer value for the parameter you want
 function AbstractState_keyed_output(handle::Clong, param::Clong)
-  output = ccall( (:AbstractState_keyed_output, "CoolProp"), Cdouble, (Clong,Clong,Ref{Clong},Ptr{UInt8},Clong), handle,param,errcode::RefValue{Clong,1},message_buffer::Array{Uint8,1},buffer_length)
+  output = ccall( (:AbstractState_keyed_output, "CoolProp"), Cdouble, (Clong,Clong,Ref{Clong},Ptr{UInt8},Clong), handle,param,errcode::RefValue{Clong,1},message_buffer::Array{UInt8,1},buffer_length)
   if errcode[] != 0
     if errcode[] == 1
       error("CoolProp: ", bytestring(convert(Ptr{UInt8}, pointer(message_buffer))))