diff --git a/.travis.yml b/.travis.yml
index 66f2d04..746a026 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,8 +3,11 @@ os:
   - linux
   - osx
 julia:
-  - 0.5
-  - 0.6
+  - 0.7
+  - 1.0
   - nightly
+matrix:
+  allow_failures:
+  - julia: nightly
 after_success:
-  - julia -e 'cd(Pkg.dir("FunctionWrappers")); Pkg.add("Coverage"); using Coverage; Codecov.submit(process_folder())'
+ - julia --project -e 'import Pkg; Pkg.add("Coverage"); using Coverage; Codecov.submit(Codecov.process_folder())'
diff --git a/REQUIRE b/REQUIRE
index 94237c0..cdbb2dc 100644
--- a/REQUIRE
+++ b/REQUIRE
@@ -1 +1 @@
-julia 0.5
+julia 0.7-alpha
diff --git a/appveyor.yml b/appveyor.yml
index 48d7358..964272f 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,15 +1,21 @@
 environment:
   matrix:
-  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x86/0.5/julia-0.5-latest-win32.exe"
-  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x64/0.5/julia-0.5-latest-win64.exe"
-  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x86/0.6/julia-0.6-latest-win32.exe"
-  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x64/0.6/julia-0.6-latest-win64.exe"
-  - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x86/julia-latest-win32.exe"
-  - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x64/julia-latest-win64.exe"
+  - julia_version: 0.7
+  - julia_version: 1
+  - julia_version: nightly
+
+platform:
+  - x86 # 32-bit
+  - x64 # 64-bit
+
+matrix:
+  allow_failures:
+  - julia_version: latest
 
 branches:
   only:
     - master
+    - /release-.*/
 
 notifications:
   - provider: Email
@@ -18,22 +24,18 @@ notifications:
     on_build_status_changed: false
 
 install:
-  - ps: "[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12"
-# if there's a newer build queued for the same PR, cancel this one
-  - ps: if ($env:APPVEYOR_PULL_REQUEST_NUMBER -and $env:APPVEYOR_BUILD_NUMBER -ne ((Invoke-RestMethod `
-        https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG/history?recordsNumber=50).builds | `
-        Where-Object pullRequestId -eq $env:APPVEYOR_PULL_REQUEST_NUMBER)[0].buildNumber) { `
-        throw "There are newer queued builds for this pull request, failing early." }
-# Download most recent Julia Windows binary
-  - ps: (new-object net.webclient).DownloadFile(
-        $env:JULIA_URL,
-        "C:\projects\julia-binary.exe")
-# Run installer silently, output to C:\projects\julia
-  - C:\projects\julia-binary.exe /S /D=C:\projects\julia
+  - ps: iex ((new-object net.webclient).DownloadString("https://raw.githubusercontent.com/JuliaCI/Appveyor.jl/version-1/bin/install.ps1"))
 
 build_script:
-  - C:\projects\julia\bin\julia -e "versioninfo();
-      Pkg.clone(pwd(), \"FunctionWrappers\"); Pkg.build(\"FunctionWrappers\")"
+  - echo "%JL_BUILD_SCRIPT%"
+  - C:\julia\bin\julia -e "%JL_BUILD_SCRIPT%"
 
 test_script:
-  - C:\projects\julia\bin\julia --check-bounds=yes -e "Pkg.test(\"FunctionWrappers\")"
+  - echo "%JL_TEST_SCRIPT%"
+  - C:\julia\bin\julia -e "%JL_TEST_SCRIPT%"
+
+# # Uncomment to support code coverage upload. Should only be enabled for packages
+# # which would have coverage gaps without running on Windows
+# on_success:
+#   - echo "%JL_CODECOV_SCRIPT%"
+#   - C:\julia\bin\julia -e "%JL_CODECOV_SCRIPT%"
diff --git a/src/FunctionWrappers.jl b/src/FunctionWrappers.jl
index 3f3483e..9e4d004 100644
--- a/src/FunctionWrappers.jl
+++ b/src/FunctionWrappers.jl
@@ -11,89 +11,87 @@ module FunctionWrappers
                    %v = trunc i8 %0 to i1
                    call void @llvm.assume(i1 %v)
                    ret void
-                   """), Void, Tuple{Bool}, v)
+                   """), Cvoid, Tuple{Bool}, v)
 end
 
-@static if isdefined(Base, Symbol("@nospecialize"))
-    is_singleton(@nospecialize(T)) = isdefined(T, :instance)
-else
-    is_singleton(T::ANY) = isdefined(T, :instance)
-end
+is_singleton(@nospecialize(T)) = isdefined(T, :instance)
 
 # Convert return type and generates cfunction signatures
 Base.@pure map_rettype(T) =
-    (isbits(T) || T === Any || is_singleton(T)) ? T : Ref{T}
+    (isbitstype(T) || T === Any || is_singleton(T)) ? T : Ref{T}
 Base.@pure function map_cfunc_argtype(T)
     if is_singleton(T)
         return Ref{T}
     end
-    return (isbits(T) || T === Any) ? T : Ref{T}
+    return (isbitstype(T) || T === Any) ? T : Ref{T}
 end
 Base.@pure function map_argtype(T)
     if is_singleton(T)
         return Any
     end
-    return (isbits(T) || T === Any) ? T : Any
+    return (isbitstype(T) || T === Any) ? T : Any
 end
-Base.@pure get_cfunc_argtype(Obj, Args) =
-    Tuple{Ref{Obj}, (map_cfunc_argtype(Arg) for Arg in Args.parameters)...}
-
-# Call wrapper since `cfunction` does not support non-function
-# or closures
-if VERSION >= v"0.6.0"
-    # Can in princeple be lower but 0.6 doesn't warn on this so it doesn't matter
-    eval(parse("struct CallWrapper{Ret} <: Function end"))
-else
-    include_string("immutable CallWrapper{Ret} <: Function end")
+
+# callable that converts output of f to type Ret
+struct CallWrapper{Ret, F}
+    f::F
 end
-(::CallWrapper{Ret}){Ret}(f, args...)::Ret = f(args...)
 
-# Specialized wrapper for
+CallWrapper{Ret}(f::F) where {Ret, F} = CallWrapper{Ret, F}(f)
+
+(wrapper::CallWrapper{Ret})(args...) where {Ret} = convert(Ret, wrapper.f(args...))
+
 for nargs in 0:128
-    @eval (::CallWrapper{Ret}){Ret}(f, $((Symbol("arg", i) for i in 1:nargs)...))::Ret =
-        f($((Symbol("arg", i) for i in 1:nargs)...))
+    @eval function (wrapper::CallWrapper{Ret})($((Symbol("arg", i) for i in 1:nargs)...)) where Ret
+        convert(Ret, wrapper.f($((Symbol("arg", i) for i in 1:nargs)...)))
+    end
 end
 
-let ex = if VERSION >= v"0.6.0"
-    # Can in princeple be lower but 0.6 doesn't warn on this so it doesn't matter
-    parse("mutable struct FunctionWrapper{Ret,Args<:Tuple} end")
-else
-    parse("type FunctionWrapper{Ret,Args<:Tuple} end")
+@generated function make_cfunction(obj::objT, ::Type{Ret}, ::Type{Args}) where {objT,Ret,Args}
+    quote
+        wrapped = CallWrapper{Ret}(obj)
+        @cfunction(
+            $(Expr(:$, :wrapped)), # use $ to create runtime closure over obj
+            map_rettype(Ret),
+            ($([:(map_cfunc_argtype($Arg)) for Arg in Args.parameters]...), ))
+    end
 end
-    ex.args[3] = quote
-        ptr::Ptr{Void}
-        objptr::Ptr{Void}
-        obj
-        objT
-        function (::Type{FunctionWrapper{Ret,Args}}){Ret,Args,objT}(obj::objT)
-            objref = Base.cconvert(Ref{objT}, obj)
-            new{Ret,Args}(cfunction(CallWrapper{Ret}(), map_rettype(Ret),
-                                    get_cfunc_argtype(objT, Args)),
-                          Base.unsafe_convert(Ref{objT}, objref), objref, objT)
-        end
-        (::Type{FunctionWrapper{Ret,Args}}){Ret,Args}(obj::FunctionWrapper{Ret,Args}) = obj
+
+mutable struct FunctionWrapper{Ret,Args<:Tuple}
+    ptr::Ptr{Cvoid}
+    objptr::Ptr{Cvoid}
+    cfun
+    obj
+    objT
+    function FunctionWrapper{Ret,Args}(obj::objT) where {Ret,Args,objT}
+        cfun = make_cfunction(obj, Ret, Args)
+        ptr = Base.unsafe_convert(Ptr{Cvoid}, Base.cconvert(Ptr{Cvoid}, cfun))
+        objptr = Base.unsafe_convert(Ref{objT}, Base.cconvert(Ref{objT}, obj))
+        new{Ret,Args}(ptr, objptr, cfun, obj, objT)
     end
-    eval(ex)
+
+    FunctionWrapper{Ret,Args}(obj::FunctionWrapper{Ret,Args}) where {Ret,Args} = obj
 end
 
-Base.convert{T<:FunctionWrapper}(::Type{T}, obj) = T(obj)
-Base.convert{T<:FunctionWrapper}(::Type{T}, obj::T) = obj
+Base.convert(::Type{T}, obj) where {T<:FunctionWrapper} = T(obj)
+Base.convert(::Type{T}, obj::T) where {T<:FunctionWrapper} = obj
 
-@noinline function reinit_wrapper{Ret,Args}(f::FunctionWrapper{Ret,Args})
-    objref = f.obj
+@noinline function reinit_wrapper(f::FunctionWrapper{Ret,Args}) where {Ret,Args}
+    obj = f.obj
     objT = f.objT
-    ptr = cfunction(CallWrapper{Ret}(), map_rettype(Ret),
-                    get_cfunc_argtype(objT, Args))
+    cfun = make_cfunction(obj, Ret, Args)
+    ptr = Base.unsafe_convert(Ptr{Cvoid}, Base.cconvert(Ptr{Cvoid}, cfun))
     f.ptr = ptr
-    f.objptr = Base.unsafe_convert(Ref{objT}, objref)
-    return ptr
+    f.objptr = Base.unsafe_convert(Ref{objT}, Base.cconvert(Ref{objT}, obj))
+    f.cfun = cfun
+    return ptr::Ptr{Cvoid}
 end
 
-@generated function do_ccall{Ret,Args}(f::FunctionWrapper{Ret,Args}, args::Args)
+@generated function do_ccall(f::FunctionWrapper{Ret,Args}, args::Args) where {Ret,Args}
     # Has to be generated since the arguments type of `ccall` does not allow
     # anything other than tuple (i.e. `@pure` function doesn't work).
     quote
-        $(Expr(:meta, :inline))
+        Base.@_inline_meta
         ptr = f.ptr
         if ptr == C_NULL
             # For precompile support
@@ -102,8 +100,8 @@ end
         assume(ptr != C_NULL)
         objptr = f.objptr
         ccall(ptr, $(map_rettype(Ret)),
-              (Ptr{Void}, $((map_argtype(Arg) for Arg in Args.parameters)...)),
-              objptr, $((:(args[$i]) for i in 1:length(Args.parameters))...))
+              ($((map_argtype(Arg) for Arg in Args.parameters)...),),
+              $((:(args[$i]) for i in 1:length(Args.parameters))...))
     end
 end
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 1658bf7..242b4e9 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -2,15 +2,13 @@
 
 import FunctionWrappers
 import FunctionWrappers: FunctionWrapper
-using Base.Test
+using Test
 
-if VERSION >= v"0.6.0"
-    # Can in princeple be lower but 0.6 doesn't warn on this so it doesn't matter
-    eval(parse("struct CallbackF64 f::FunctionWrapper{Float64,Tuple{Int}} end"))
-else
-    eval(parse("immutable CallbackF64 f::FunctionWrapper{Float64,Tuple{Int}} end"))
+struct CallbackF64
+    f::FunctionWrapper{Float64,Tuple{Int}}
 end
 (cb::CallbackF64)(v) = cb.f(v)
+
 gen_closure(x) = y->x + y
 
 @testset "As field" begin
@@ -56,10 +54,10 @@ end
     @test FunctionWrappers.identityAnyAny(1) === 1
 end
 
-@testset "Void" begin
-    identityVoidVoid = FunctionWrapper{Void,Tuple{Void}}(identity)
-    @test identityVoidVoid(nothing) === nothing
+@testset "Nothing" begin
+    identityNothingNothing = FunctionWrapper{Nothing,Tuple{Nothing}}(identity)
+    @test identityNothingNothing(nothing) === nothing
     f1 = (a, b)->b
-    fIntVoidInt = FunctionWrapper{Int,Tuple{Void,Int}}(f1)
-    @test fIntVoidInt(nothing, 1) === 1
+    fIntNothingInt = FunctionWrapper{Int,Tuple{Nothing,Int}}(f1)
+    @test fIntNothingInt(nothing, 1) === 1
 end