diff --git a/.travis.yml b/.travis.yml
index 1b8ea91..b805f4d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,8 +3,8 @@ os:
     - osx
     - linux
 julia:
-    - 0.4
     - 0.5
+    - 0.6
     - nightly
 notifications:
     email: false
diff --git a/REQUIRE b/REQUIRE
index 7274a2c..6463e31 100644
--- a/REQUIRE
+++ b/REQUIRE
@@ -1,2 +1,2 @@
-julia 0.4
+julia 0.5
 Compat 0.24.0
diff --git a/appveyor.yml b/appveyor.yml
index bfd78e7..57d4bfa 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,9 +1,9 @@
 environment:
   matrix:
-  - JULIAVERSION: "julialang/bin/winnt/x86/0.4/julia-0.4-latest-win32.exe"
-  - JULIAVERSION: "julialang/bin/winnt/x64/0.4/julia-0.4-latest-win64.exe"
   - JULIAVERSION: "julialang/bin/winnt/x86/0.5/julia-0.5-latest-win32.exe"
   - JULIAVERSION: "julialang/bin/winnt/x64/0.5/julia-0.5-latest-win64.exe"
+  - JULIAVERSION: "julialang/bin/winnt/x86/0.6/julia-0.6-latest-win32.exe"
+  - JULIAVERSION: "julialang/bin/winnt/x64/0.6/julia-0.6-latest-win64.exe"
   - JULIAVERSION: "julianightlies/bin/winnt/x86/julia-latest-win32.exe"
   - JULIAVERSION: "julianightlies/bin/winnt/x64/julia-latest-win64.exe"
 
diff --git a/src/Parser.jl b/src/Parser.jl
index d6938e6..941aea1 100644
--- a/src/Parser.jl
+++ b/src/Parser.jl
@@ -123,7 +123,7 @@ end
 
 # Throws an error message with an indicator to the source
 function _error(message::AbstractString, ps::MemoryParserState)
-    orig = Compat.UTF8String(ps.utf8data)
+    orig = String(ps.utf8data)
     lines = _count_before(orig, '\n', ps.s)
     # Replace all special multi-line/multi-space characters with a space.
     strnl = replace(orig, r"[\b\f\n\r\t\s]", " ")
@@ -279,7 +279,7 @@ function parse_string(ps::ParserState)
         elseif c < SPACE
             _error(E_BAD_CONTROL, ps)
         elseif c == STRING_DELIM
-            return Compat.UTF8String(b)
+            return String(b)
         end
 
         push!(b, c)
@@ -366,12 +366,12 @@ end
 
 
 function unparameterize_type{T}(::Type{T})
-    candidate = typeintersect(T, Associative{Compat.UTF8String, Any})
+    candidate = typeintersect(T, Associative{String, Any})
     candidate <: Union{} ? T : candidate
 end
 
-function parse{T<:Associative}(str::AbstractString; dicttype::Type{T}=Dict{Compat.UTF8String,Any})
-    ps = MemoryParserState(Vector{UInt8}(Compat.UTF8String(str)), 1)
+function parse{T<:Associative}(str::AbstractString; dicttype::Type{T}=Dict{String,Any})
+    ps = MemoryParserState(Vector{UInt8}(String(str)), 1)
     v = parse_value(ps, unparameterize_type(T))
     chomp_space!(ps)
     if hasmore(ps)
@@ -380,15 +380,15 @@ function parse{T<:Associative}(str::AbstractString; dicttype::Type{T}=Dict{Compa
     v
 end
 
-function parse{T<:Associative}(io::IO; dicttype::Type{T}=Dict{Compat.UTF8String,Any})
+function parse{T<:Associative}(io::IO; dicttype::Type{T}=Dict{String,Any})
     ps = StreamingParserState(io)
     parse_value(ps, unparameterize_type(T))
 end
 
-function parsefile{T<:Associative}(filename::AbstractString; dicttype::Type{T}=Dict{Compat.UTF8String, Any}, use_mmap=true)
+function parsefile{T<:Associative}(filename::AbstractString; dicttype::Type{T}=Dict{String, Any}, use_mmap=true)
     sz = filesize(filename)
     open(filename) do io
-        s = use_mmap ? Compat.UTF8String(Mmap.mmap(io, Vector{UInt8}, sz)) : readstring(io)
+        s = use_mmap ? String(Mmap.mmap(io, Vector{UInt8}, sz)) : readstring(io)
         parse(s; dicttype=dicttype)
     end
 end
diff --git a/src/Writer.jl b/src/Writer.jl
index c686215..374d1db 100644
--- a/src/Writer.jl
+++ b/src/Writer.jl
@@ -43,13 +43,7 @@ function lower(a)
     end
 end
 
-if isdefined(Base, :Dates)
-    lower(s::Base.Dates.TimeType) = string(s)
-end
-
-if VERSION < v"0.5.0-dev+2396"
-    lower(f::Function) = "function at $(f.fptr)"
-end
+lower(s::Base.Dates.TimeType) = string(s)
 
 # To avoid allocating an intermediate string, we directly define `show_json`
 # for this type instead of lowering it to a string first (which would
@@ -258,7 +252,7 @@ end
 function show_json(io::SC, s::CS, x::Union{Integer, AbstractFloat})
     # workaround for issue in Julia 0.5.x where Float32 values are printed as
     # 3.4f-5 instead of 3.4e-5
-    @static if v"0.5-" <= VERSION < v"0.6.0-dev.788"
+    @static if VERSION < v"0.6.0-dev.788"
         if isa(x, Float32)
             return show_json(io, s, Float64(x))
         end
@@ -313,7 +307,7 @@ function show_json{T,n}(io::SC, s::CS, A::AbstractArray{T,n})
     begin_array(io)
     newdims = ntuple(_ -> :, Val{n - 1})
     for j in 1:size(A, n)
-        show_element(io, s, Compat.view(A, newdims..., j))
+        show_element(io, s, view(A, newdims..., j))
     end
     end_array(io)
 end
diff --git a/src/specialized.jl b/src/specialized.jl
index 4f759d1..7738c37 100644
--- a/src/specialized.jl
+++ b/src/specialized.jl
@@ -20,7 +20,7 @@ function parse_string(ps::MemoryParserState)
         parse_string(ps, b)
     end
 
-    Compat.UTF8String(b)
+    String(b)
 end
 
 """
diff --git a/test/lowering.jl b/test/lowering.jl
index 6aae3eb..deca632 100644
--- a/test/lowering.jl
+++ b/test/lowering.jl
@@ -4,7 +4,6 @@ using JSON
 using Base.Test
 using Compat
 using FixedPointNumbers: Fixed
-import Compat: String
 
 if isdefined(Base, :Dates)
     @test JSON.json(Date(2016, 8, 3)) == "\"2016-08-03\""
diff --git a/test/runtests.jl b/test/runtests.jl
index df46a7b..c1f28b0 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,7 +1,6 @@
 using JSON
 using Base.Test
 using Compat
-import Compat: String
 
 import DataStructures
 
@@ -24,9 +23,9 @@ validate_c(c) = begin
 validate_e(e) = begin
                     j=JSON.parse(e)
                     @test j != nothing
-                    @test typeof(j) == Dict{Compat.UTF8String, Any}
+                    @test typeof(j) == Dict{String, Any}
                     @test length(j) == 1
-                    @test typeof(j["menu"]) == Dict{Compat.UTF8String, Any}
+                    @test typeof(j["menu"]) == Dict{String, Any}
                     @test length(j["menu"]) == 2
                     @test j["menu"]["header"] == "SVG\tViewerα"
                     @test isa(j["menu"]["items"], Vector{Any})
@@ -50,11 +49,7 @@ validate_unicode(unicode) = begin
                             end
 # -------
 
-if VERSION >= v"0.5.0-dev+1343"
-    finished_async_tests = RemoteChannel()
-else
-    finished_async_tests = RemoteRef()
-end
+finished_async_tests = RemoteChannel()
 
 @async begin
     s = listen(7777)
@@ -174,7 +169,7 @@ json_zeros = json(zeros)
 
 
 # Printing an empty array or Dict shouldn't cause a BoundsError
-@test json(Compat.ASCIIString[]) == "[]"
+@test json(String[]) == "[]"
 @test json(Dict()) == "{}"
 
 #test for issue 26
@@ -274,10 +269,6 @@ end
 @test Float32(JSON.parse(json(2.1f-8))) == 2.1f-8
 
 # Check printing of more exotic objects
-if VERSION < v"0.5.0-dev+2396"
-    # Test broken in v0.5, code is using internal structure of Function type!
-    @test sprint(JSON.print, sprint) == string("\"function at ", sprint.fptr, "\"")
-end
 @test sprint(JSON.print, Float64) == string("\"Float64\"")
 @test_throws ArgumentError sprint(JSON.print, JSON)
 
diff --git a/test/serializer.jl b/test/serializer.jl
index 98fd2e9..57f0dbe 100644
--- a/test/serializer.jl
+++ b/test/serializer.jl
@@ -3,7 +3,6 @@ module TestSerializer
 using JSON
 using Base.Test
 using Compat
-import Compat: String
 
 # to define a new serialization behaviour, import these first
 import JSON.Serializations: CommonSerialization, StandardSerialization
@@ -45,7 +44,7 @@ JSON.show_json(io::SC, ::NaNSerialization, f::AbstractFloat) =
 # issue #170: Print JavaScript functions directly
 immutable JSSerialization <: CS end
 immutable JSFunction
-    data::Compat.UTF8String
+    data::String
 end
 
 function JSON.show_json(io::SC, ::JSSerialization, f::JSFunction)