diff --git a/tools/files.js b/tools/files.js
index 840fd955c7..2760384767 100644
--- a/tools/files.js
+++ b/tools/files.js
@@ -573,7 +573,7 @@ if (! process.env.METEOR_SAVE_TMPDIRS) {
 // the archive should contain a single top-level directory, which will
 // be renamed atomically to destPath. The entire tree will be made
 // readonly.
-files.extractTarGz = function (buffer, destPath) {
+files.extractTarGz = function (buffer, destPath, options) {
   var parentDir = files.pathDirname(destPath);
   var tempDir = files.pathJoin(parentDir, '.tmp' + utils.randomToken());
   files.mkdir_p(tempDir);
@@ -589,7 +589,7 @@ files.extractTarGz = function (buffer, destPath) {
 
   var extractor = new tar.Extract({ path: convertToOSPath(tempDir) })
     .on('entry', function (e) {
-      if (process.platform === "win32") {
+      if (process.platform === "win32" || options.forceConvert) {
         // On Windows, try to convert old packages that have colons in paths
         // by blindly replacing all of the paths. Otherwise, we can't exen
         // extract the tarball
diff --git a/tools/tests/built-packages/has-colons.tgz b/tools/tests/built-packages/has-colons.tgz
index a15458ef43..02278cafda 100644
Binary files a/tools/tests/built-packages/has-colons.tgz and b/tools/tests/built-packages/has-colons.tgz differ
diff --git a/tools/tests/colon-converter-tests.js b/tools/tests/colon-converter-tests.js
index 9e951bf0b7..58df80b119 100644
--- a/tools/tests/colon-converter-tests.js
+++ b/tools/tests/colon-converter-tests.js
@@ -93,3 +93,23 @@ if (process.platform !== "win32") {
 // Tests step 3: check if old packages are converted properly to have no weird
 // paths for Windows
 
+selftest.define("package with colons is converted on Windows", function () {
+  // We have a built package tarball in the git repo
+  var tarballPath = files.pathJoin(files.convertToStandardPath(__dirname),
+    "built-packages", "has-colons.tgz");
+
+  // Unpack it using our tropohouse code
+  var tarball = files.readFile(tarballPath);
+
+  // Force conversion of file paths with second argument
+  var targetDirectory = tropohouse._extractAndConvert(tarball, true);
+
+  // Uncomment below to check results
+  // console.log(utils.execFileSync("find", [targetDirectory], {
+  //   cwd: targetDirectory
+  // }).stdout);
+  
+  // Saved tree hash of the correct result
+  selftest.expectEqual(files.treeHash(targetDirectory),
+    "AQX/7h0fXwHT9rNQvlBTvIZAE2g8krlnkEQMc9lTuMI=");
+});
diff --git a/tools/tropohouse.js b/tools/tropohouse.js
index b4666d60bd..714a210aa3 100644
--- a/tools/tropohouse.js
+++ b/tools/tropohouse.js
@@ -38,13 +38,16 @@ exports.default = new exports.Tropohouse(defaultWarehouseDir());
 /**
  * Extract a package tarball, and on Windows convert file paths and metadata
  * @param  {String} packageTarball path to tarball
+ * @param {Boolean} forceConvert Convert paths even on unix, for testing
  * @return {String}                Temporary directory with contents of package
  */
-exports._extractAndConvert = function (packageTarball) {
+exports._extractAndConvert = function (packageTarball, forceConvert) {
   var targetDirectory = files.mkdtemp();
-  files.extractTarGz(packageTarball, targetDirectory);
+  files.extractTarGz(packageTarball, targetDirectory, {
+    forceConvert: forceConvert
+  });
 
-  if (process.platform === "win32") {
+  if (process.platform === "win32" || forceConvert) {
     // Packages published before the Windows release might have colons or
     // other unsavory characters in path names. In hopes of making most of
     // these packages work on Windows, we will try to automatically convert
@@ -59,7 +62,6 @@ exports._extractAndConvert = function (packageTarball) {
     // file paths. We have already converted the colons in the actual files
     // while untarring.
     var metadata = Isopack.readMetadataFromDirectory(targetDirectory);
-    console.log(files.readdir(targetDirectory));
     var convertedMetadata = colonConverter.convertIsopack(metadata);
 
     // Step 2. Write the isopack.json file
@@ -97,6 +99,26 @@ exports._extractAndConvert = function (packageTarball) {
       // Result: Now we are in a state where the unibuild file paths are
       // consistent with the paths in the downloaded tarball.
     });
+
+    // Lastly, convert the build plugins, which are in the JSImage format
+    _.each(metadata.plugins, function (pluginMeta) {
+      var programJsonPath = files.pathJoin(targetDirectory, pluginMeta.path);
+      var programJson = JSON.parse(files.readFile(programJsonPath));
+
+      if (programJson.format !== "javascript-image-pre1") {
+        throw new Error("Unsupported plugin format: " +
+          JSON.stringify(programJson.format));
+      }
+
+      var convertedPlugin = colonConverter.convertJSImage(programJson);
+
+      files.chmod(programJsonPath, 0777);
+      files.writeFile(programJsonPath,
+        new Buffer(JSON.stringify(convertedPlugin, null, 2), 'utf8'),
+        {mode: 0444});
+      // Result: Now we are in a state where the build plugin file paths are
+      // consistent with the paths in the downloaded tarball.
+    });
   }
 
   return targetDirectory;