diff --git a/LibGit2Sharp.Tests/SubstitutionCipherFilterFixture.cs b/LibGit2Sharp.Tests/FilterSubstitutionCipherFixture.cs
similarity index 98%
rename from LibGit2Sharp.Tests/SubstitutionCipherFilterFixture.cs
rename to LibGit2Sharp.Tests/FilterSubstitutionCipherFixture.cs
index 39ccf1f5b..f2fc14b66 100644
--- a/LibGit2Sharp.Tests/SubstitutionCipherFilterFixture.cs
+++ b/LibGit2Sharp.Tests/FilterSubstitutionCipherFixture.cs
@@ -6,7 +6,7 @@
 
 namespace LibGit2Sharp.Tests
 {
-    public class SubstitutionCipherFilterFixture : BaseFixture
+    public class FilterSubstitutionCipherFixture : BaseFixture
     {
         [Fact]
         public void CorrectlyEncodesAndDecodesInput()
diff --git a/LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj b/LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj
index 6f5f64e63..21bf7faba 100644
--- a/LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj
+++ b/LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj
@@ -96,7 +96,7 @@
     <Compile Include="ResetIndexFixture.cs" />
     <Compile Include="SmartSubtransportFixture.cs" />
     <Compile Include="StatusFixture.cs" />
-    <Compile Include="SubstitutionCipherFilterFixture.cs" />
+    <Compile Include="FilterSubstitutionCipherFixture.cs" />
     <Compile Include="TestHelpers\BaseFixture.cs" />
     <Compile Include="BlobFixture.cs" />
     <Compile Include="BranchFixture.cs" />
diff --git a/LibGit2Sharp.Tests/TestHelpers/SubstitutionCipherFilter.cs b/LibGit2Sharp.Tests/TestHelpers/SubstitutionCipherFilter.cs
index 25a90be4c..184ca526e 100644
--- a/LibGit2Sharp.Tests/TestHelpers/SubstitutionCipherFilter.cs
+++ b/LibGit2Sharp.Tests/TestHelpers/SubstitutionCipherFilter.cs
@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.IO;
-using System.Text;
 
 namespace LibGit2Sharp.Tests.TestHelpers
 {
@@ -35,27 +34,23 @@ protected override int Smudge(string path, Stream input, Stream output)
 
         public static int RotateByThirteenPlaces(Stream input, Stream output)
         {
+            int value;
 
-            using (var streamReader = new StreamReader(input, Encoding.UTF8))
+            while ((value = input.ReadByte()) != -1)
             {
-                var inputString = streamReader.ReadToEnd();
-                char[] array = inputString.ToCharArray();
-                for (int i = 0; i < inputString.Length; i++)
+                if ((value >= 'a' && value <= 'm') || (value >= 'A' && value <= 'M'))
                 {
-                    var value = inputString[i];
-                    if ((value >= 'a' && value <= 'm') || (value >= 'A' && value <= 'M'))
-                        array[i] = (char)(value + 13);
-                    else if ((value >= 'n' && value <= 'z') || (value >= 'N' && value <= 'Z'))
-                        array[i] = (char)(value - 13);
+                    value += 13;
                 }
-
-                using (var streamWriter = new StreamWriter(output, Encoding.UTF8))
+                else if ((value >= 'n' && value <= 'z') || (value >= 'N' && value <= 'Z'))
                 {
-                    streamWriter.Write(array);
+                    value -= 13;
                 }
 
-                return 0;
+                output.WriteByte((byte)value);
             }
+
+            return 0;
         }
     }
 }
diff --git a/LibGit2Sharp/Core/GitBufWriteStream.cs b/LibGit2Sharp/Core/GitBufWriteStream.cs
index f727fec1e..7cc281f22 100644
--- a/LibGit2Sharp/Core/GitBufWriteStream.cs
+++ b/LibGit2Sharp/Core/GitBufWriteStream.cs
@@ -13,7 +13,7 @@ internal GitBufWriteStream(IntPtr gitBufPointer)
             this.gitBufPointer = gitBufPointer;
 
             //Preallocate the buffer
-            Proxy.git_buf_grow(gitBufPointer, 1024);
+            Proxy.git_buf_grow(gitBufPointer, 4096);
         }
 
         public override void Flush()
@@ -37,32 +37,9 @@ public override int Read(byte[] buffer, int offset, int count)
 
         public override void Write(byte[] buffer, int offset, int count)
         {
-            AutoGrowBuffer(count);
-
             Proxy.git_buf_put(gitBufPointer, buffer, offset, count);
         }
 
-        private void AutoGrowBuffer(int count)
-        {
-            var gitBuf = gitBufPointer.MarshalAs<GitBuf>();
-
-            var ulongCount = Convert.ToUInt64(count);
-            var asize = (ulong)gitBuf.asize;
-            var size = (ulong)gitBuf.size;
-
-            var isBufferLargeEnoughToHoldTheNewData = (asize - size) > ulongCount;
-            var filledBufferPercentage = (100.0 * size / asize);
-
-            if (isBufferLargeEnoughToHoldTheNewData && filledBufferPercentage < 90)
-            {
-                return;
-            }
-
-            var targetSize = (ulong)(1.5 * (asize + ulongCount));
-
-            Proxy.git_buf_grow(gitBufPointer, targetSize);
-        }
-
         public override bool CanRead
         {
             get { return false; }
diff --git a/LibGit2Sharp/Filter.cs b/LibGit2Sharp/Filter.cs
index 596b8feb0..5697d7d6c 100644
--- a/LibGit2Sharp/Filter.cs
+++ b/LibGit2Sharp/Filter.cs
@@ -237,10 +237,11 @@ int ApplyCallback(GitFilter gitFilter, IntPtr payload,
             var filterSource = FilterSource.FromNativePtr(filterSourcePtr);
             using (var reader = new GitBufReadStream(gitBufferFromPtr))
             using (var writer = new GitBufWriteStream(gitBufferToPtr))
+            using (var bufferedWriter = new BufferedStream(writer))
             {
                 return filterSource.SourceMode == FilterMode.Clean ?
-                    Clean(filterSource.Path, reader, writer) :
-                    Smudge(filterSource.Path, reader, writer);
+                    Clean(filterSource.Path, reader, bufferedWriter) :
+                    Smudge(filterSource.Path, reader, bufferedWriter);
             }
         }
     }