diff --git a/CKAN/CKAN/ModuleInstaller.cs b/CKAN/CKAN/ModuleInstaller.cs
index cf6d02adf1..f3608aa63a 100644
--- a/CKAN/CKAN/ModuleInstaller.cs
+++ b/CKAN/CKAN/ModuleInstaller.cs
@@ -6,6 +6,7 @@
 using System.Security.Cryptography;
 using System.Text.RegularExpressions;
 using System.Threading;
+using ICSharpCode.SharpZipLib.Core;
 using ICSharpCode.SharpZipLib.Zip;
 using System.Transactions;
 using ChinhDo.Transactions;
@@ -755,11 +756,17 @@ internal static void CopyZipEntry(ZipFile zipfile, ZipEntry entry, string fullPa
                     file_transaction.CreateDirectory(directory);
                 }
 
+                // Snapshot whatever was there before. If there's nothing, this will just
+                // remove our file on rollback.
+                file_transaction.Snapshot(fullPath);
+
                 // It's a file! Prepare the streams
                 using (Stream zipStream = zipfile.GetInputStream(entry))
-                using (StreamReader reader = new StreamReader(zipStream))
+                using (FileStream writer = File.Create(fullPath))
                 {
-                    file_transaction.WriteAllText(fullPath, reader.ReadToEnd());
+                    // 4k is the block size on practically every disk and OS.
+                    byte[] buffer = new byte[4096];
+                    StreamUtils.Copy(zipStream, writer, buffer);
                 }
             }
 
diff --git a/CKAN/Tests/CKAN/ModuleInstaller.cs b/CKAN/Tests/CKAN/ModuleInstaller.cs
index e3a1ce2d73..4547bce264 100644
--- a/CKAN/Tests/CKAN/ModuleInstaller.cs
+++ b/CKAN/Tests/CKAN/ModuleInstaller.cs
@@ -1,6 +1,7 @@
 using NUnit.Framework;
 using System;
 using System.IO;
+using System.Transactions;
 using System.Collections.Generic;
 using ICSharpCode.SharpZipLib.Zip;
 using CKAN;
@@ -100,14 +101,9 @@ public void No_Installable_Files()
         // GH #205, make sure we write in *binary*, not text.
         public void BinaryNotText_205()
         {
-            string dogezip = Tests.TestData.DogeCoinFlagZip();
-            ZipFile zipfile = new ZipFile(dogezip);
-
-            ZipEntry entry = zipfile.GetEntry("DogeCoinFlag-1.01/GameData/DogeCoinFlag/Flags/dogecoin.png");
-            string tmpfile = Path.GetTempFileName();
-
-            CKAN.ModuleInstaller.CopyZipEntry(zipfile, entry, tmpfile, false);
-
+            // Use CopyZipEntry (via CopyDogeFromZip) and make sure it
+            // comes out the right size.
+            string tmpfile = CopyDogeFromZip();
             long size = new System.IO.FileInfo(tmpfile).Length;
 
             try
@@ -122,6 +118,38 @@ public void BinaryNotText_205()
             }
         }
 
+        [Test()]
+        // Make sure when we roll-back a transaction, files written with CopyZipEntry go
+        // back to their pre-transaction state.
+        public void FileSysRollBack()
+        {
+            string file;
+
+            using (var scope = new TransactionScope())
+            {
+                file = CopyDogeFromZip();
+                Assert.IsTrue(new System.IO.FileInfo(file).Length > 0);
+                scope.Dispose(); // Rollback
+            }
+
+            // CopyDogeFromZip creates a tempfile, so we check to make sure it's empty
+            // again on transaction rollback.
+            Assert.AreEqual(0, new System.IO.FileInfo(file).Length);
+        }
+
+        private static string CopyDogeFromZip()
+        {
+            string dogezip = Tests.TestData.DogeCoinFlagZip();
+            ZipFile zipfile = new ZipFile(dogezip);
+
+            ZipEntry entry = zipfile.GetEntry("DogeCoinFlag-1.01/GameData/DogeCoinFlag/Flags/dogecoin.png");
+            string tmpfile = Path.GetTempFileName();
+
+            CKAN.ModuleInstaller.CopyZipEntry(zipfile, entry, tmpfile, false);
+
+            return tmpfile;
+        }
+
         private void TestDogeCoinStanza(ModuleInstallDescriptor stanza)
         {
             Assert.AreEqual("GameData", stanza.install_to);
diff --git a/CKAN/Tests/Tests.csproj b/CKAN/Tests/Tests.csproj
index e560f9fcd0..e70028958a 100644
--- a/CKAN/Tests/Tests.csproj
+++ b/CKAN/Tests/Tests.csproj
@@ -39,6 +39,7 @@
     <Reference Include="ICSharpCode.SharpZipLib">
       <HintPath>..\packages\SharpZipLib.0.86.0\lib\20\ICSharpCode.SharpZipLib.dll</HintPath>
     </Reference>
+    <Reference Include="System.Transactions" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="TestData.cs" />