diff --git a/.travis.yml b/.travis.yml
index b3d6bd2..fc3caa3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,7 +10,6 @@ os:
   - linux
 
 julia:
-  - 0.6
   - 1.0
   - nightly
 
diff --git a/appveyor.yml b/appveyor.yml
index c1edd1a..1016f07 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,7 +1,5 @@
 environment:
   matrix:
-  - 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://julialang-s3.julialang.org/bin/winnt/x86/0.7/julia-0.7-latest-win32.exe"
   - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x64/0.7/julia-0.7-latest-win64.exe"
   - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x86/julia-latest-win32.exe"
diff --git a/src/Feather.jl b/src/Feather.jl
index e918f19..43ab123 100644
--- a/src/Feather.jl
+++ b/src/Feather.jl
@@ -1,26 +1,16 @@
-VERSION < v"0.7.0-beta2.199" && __precompile__()
 module Feather
 
-using Arrow, Compat, Compat.Mmap
+using Arrow, Mmap
 using FlatBuffers, CategoricalArrays, DataStreams, DataFrames
 
-using Compat.Sys: iswindows
-
-
-if Base.VERSION < v"0.7.0-DEV.2575"
-    const Dates = Base.Dates
-    using Missings
-    using Compat: @warn
-else
-    import Dates
-end
+import Dates
 
 
 const FEATHER_VERSION = 2
 # wesm/feather/cpp/src/common.h
 const FEATHER_MAGIC_BYTES = Vector{UInt8}(codeunits("FEA1"))
 const MIN_FILE_LENGTH = 12
-const SHOULD_USE_MMAP = !iswindows()
+const SHOULD_USE_MMAP = !Sys.iswindows()
 
 
 include("metadata.jl")  # flatbuffer defintions
diff --git a/src/sink.jl b/src/sink.jl
index 2fc6144..a245930 100644
--- a/src/sink.jl
+++ b/src/sink.jl
@@ -40,11 +40,31 @@ Base.size(sink::Sink, i::Integer) = size(sink.schema, i)
 
 
 """
-    write(filename::AbstractString, df::DataFrame)
+    write(filename::AbstractString, df::DataFrame; overwrite::Bool=false)
 
 Write the dataframe `df` to the feather formatted file `filename`.
+
+If the file `filename` already exists, an error will be thrown, unless `overwrite=true` in
+which case the file will be deleted before writing.
 """
-function write(filename::AbstractString, df::AbstractDataFrame)
+function write(filename::AbstractString, df::AbstractDataFrame; overwrite::Bool=false)
+    if isfile(filename)
+        if !overwrite
+            throw(ArgumentError("File $filename already exists. Pass `overwrite=true` to overwrite."))
+        else
+            if Sys.iswindows()
+                try
+                    rm(filename)
+                catch e
+                    @error(string("Unable to delete file $filename. It's possible that it's ",
+                                  "already open and being used by this or another process."))
+                    rethrow(e)
+                end
+            else
+                rm(filename)
+            end
+        end
+    end
     sink = Feather.Sink(filename, df)
     Data.stream!(df, sink)
     Data.close!(sink)
@@ -58,7 +78,7 @@ end
 # NOTE: the below is very inefficient, but we are forced to do it by the Feather format
 function Data.streamto!(sink::Sink, ::Type{Data.Column}, val::AbstractVector{Union{T,Missing}},
                         row, col) where T
-    hasmissing = Compat.findfirst(ismissing, val)
+    hasmissing = findfirst(ismissing, val)
     sink.columns[col] = arrowformat(hasmissing == nothing ? convert(AbstractVector{T}, val) : val)
 end