diff --git a/common.js b/common.js
new file mode 100644
index 0000000..24fd323
--- /dev/null
+++ b/common.js
@@ -0,0 +1,50 @@
+var asar = require('asar')
+var child = require('child_process')
+var path = require('path')
+var rimraf = require('rimraf')
+
+module.exports = {
+  asarApp: function asarApp (finalDir, cb) {
+    var src = path.join(finalDir, 'resources', 'app')
+    var dest = path.join(finalDir, 'resources', 'app.asar')
+    asar.createPackage(src, dest, function (err) {
+      if (err) return cb(err)
+      rimraf(src, function (err) {
+        if (err) return cb(err)
+        cb(null, dest)
+      })
+    })
+  },
+
+  prune: function prune (opts, cwd, cb, nextStep) {
+    if (opts.prune) {
+      child.exec('npm prune --production', { cwd: cwd }, function pruned (err) {
+        if (err) return cb(err)
+        nextStep()
+      })
+    } else {
+      nextStep()
+    }
+  },
+
+  userIgnoreFilter: function userIgnoreFilter (opts, is_win32, finalDir) {
+    return function filter (file) {
+      if (is_win32) {
+        // convert slashes so unix-format ignores work
+        file = file.replace(/\\/g, '/')
+      }
+
+      var ignore = opts.ignore || []
+      if (!Array.isArray(ignore)) ignore = [ignore]
+      if (typeof finalDir !== 'undefined') {
+        ignore = ignore.concat([finalDir])
+      }
+      for (var i = 0; i < ignore.length; i++) {
+        if (file.match(ignore[i])) {
+          return false
+        }
+      }
+      return true
+    }
+  }
+}
diff --git a/index.js b/index.js
index 31f242c..6d5ed16 100644
--- a/index.js
+++ b/index.js
@@ -11,7 +11,7 @@ var linux = require('./linux.js')
 var win32 = require('./win32.js')
 
 module.exports = function packager (opts, cb) {
-  var packager
+  var platformPackager
   var platform = opts.platform
   var arch = opts.arch
   var version = opts.version
@@ -25,9 +25,9 @@ module.exports = function packager (opts, cb) {
   }
 
   switch (platform) {
-    case 'darwin': packager = mac; break
-    case 'linux': packager = linux; break
-    case 'win32': packager = win32; break
+    case 'darwin': platformPackager = mac; break
+    case 'linux': platformPackager = linux; break
+    case 'win32': platformPackager = win32; break
     default: return cb(new Error('Unsupported platform. Must be either darwin, linux, or win32'))
   }
 
@@ -51,7 +51,7 @@ module.exports = function packager (opts, cb) {
         if (err) return cb(err)
         extract(zipPath, {dir: tmpDir}, function (err) {
           if (err) return cb(err)
-          packager.createApp(opts, tmpDir, cb)
+          platformPackager.createApp(opts, tmpDir, cb)
         })
       })
     })
diff --git a/linux.js b/linux.js
index 4fe048d..83426c6 100644
--- a/linux.js
+++ b/linux.js
@@ -1,10 +1,8 @@
 var path = require('path')
 var fs = require('fs')
-var child = require('child_process')
 var mkdirp = require('mkdirp')
 var ncp = require('ncp').ncp
-var rimraf = require('rimraf')
-var asar = require('asar')
+var common = require('./common')
 
 module.exports = {
   createApp: function createApp (opts, templateApp, cb) {
@@ -28,16 +26,9 @@ module.exports = {
     }
 
     function copyUserApp () {
-      ncp(opts.dir, userAppDir, {filter: userFilter, dereference: true}, function copied (err) {
+      ncp(opts.dir, userAppDir, {filter: common.userIgnoreFilter(opts, false, finalDir), dereference: true}, function copied (err) {
         if (err) return cb(err)
-        if (opts.prune) {
-          prune(function pruned (err) {
-            if (err) return cb(err)
-            renameElectronBinary()
-          })
-        } else {
-          renameElectronBinary()
-        }
+        common.prune(opts, userAppDir, cb, renameElectronBinary)
       })
     }
 
@@ -45,45 +36,17 @@ module.exports = {
       fs.rename(originalBinary, finalBinary, function electronRenamed (err) {
         if (err) return cb(err)
         if (opts.asar) {
-          asarApp(cb)
+          common.asarApp(finalDir, cb)
         } else {
           cb(null, finalBinary)
         }
       })
     }
 
-    function prune (cb) {
-      child.exec('npm prune --production', { cwd: userAppDir }, cb)
-    }
-
     function appFilter (file) {
       return file.match(/default_app/) === null
     }
 
-    function userFilter (file) {
-      var ignore = opts.ignore || []
-      if (!Array.isArray(ignore)) ignore = [ignore]
-      ignore = ignore.concat([finalDir])
-      for (var i = 0; i < ignore.length; i++) {
-        if (file.match(ignore[i])) {
-          return false
-        }
-      }
-      return true
-    }
-
-    function asarApp (cb) {
-      var src = path.join(finalDir, 'resources', 'app')
-      var dest = path.join(finalDir, 'resources', 'app.asar')
-      asar.createPackage(src, dest, function (err) {
-        if (err) return cb(err)
-        rimraf(src, function (err) {
-          if (err) return cb(err)
-          cb(null, dest)
-        })
-      })
-    }
-
     copyApp()
   }
 }
diff --git a/mac.js b/mac.js
index 26ab295..b125c74 100644
--- a/mac.js
+++ b/mac.js
@@ -7,7 +7,7 @@ var plist = require('plist')
 var mkdirp = require('mkdirp')
 var rimraf = require('rimraf')
 var ncp = require('ncp').ncp
-var asar = require('asar')
+var common = require('./common')
 
 module.exports = {
   createApp: function createApp (opts, electronPath, cb) {
@@ -68,34 +68,10 @@ function buildMacApp (opts, cb, newApp) {
   fs.writeFileSync(paths.info1, plist.build(pl1))
   fs.writeFileSync(paths.info2, plist.build(pl2))
 
-  function filter (file) {
-    var ignore = opts.ignore || []
-    if (!Array.isArray(ignore)) ignore = [ignore]
-    for (var i = 0; i < ignore.length; i++) {
-      if (file.match(ignore[i])) {
-        return false
-      }
-    }
-    return true
-  }
-
   // copy users app into .app
-  ncp(opts.dir, paths.app, {filter: filter, dereference: true}, function copied (err) {
+  ncp(opts.dir, paths.app, {filter: common.userIgnoreFilter(opts), dereference: true}, function copied (err) {
     if (err) return cb(err)
 
-    if (opts.prune) {
-      prune(function pruned (err) {
-        if (err) return cb(err)
-        moveApp()
-      })
-    } else {
-      moveApp()
-    }
-
-    function prune (cb) {
-      child.exec('npm prune --production', { cwd: paths.app }, cb)
-    }
-
     function moveApp () {
       // finally, move app into cwd
       var outdir = opts.out || process.cwd()
@@ -106,7 +82,8 @@ function buildMacApp (opts, cb, newApp) {
         fs.rename(newApp, finalPath, function moved (err) {
           if (err) return cb(err)
           if (opts.asar) {
-            asarApp(function (err) {
+            var finalPath = path.join(opts.out || process.cwd(), opts.name + '.app', 'Contents', 'Resources')
+            common.asarApp(finalPath, function (err) {
               if (err) return cb(err)
               updateMacIcon(function (err) {
                 if (err) return cb(err)
@@ -135,16 +112,6 @@ function buildMacApp (opts, cb, newApp) {
       })
     }
 
-    function asarApp (cb) {
-      var finalPath = path.join(opts.out || process.cwd(), opts.name + '.app', 'Contents', 'Resources')
-      var src = path.join(finalPath, 'app')
-      var dest = path.join(finalPath, 'app.asar')
-      asar.createPackage(src, dest, function (err) {
-        if (err) return cb(err)
-        rimraf(src, cb)
-      })
-    }
-
     function codesign () {
       var appPath = path.join(opts.out || process.cwd(), opts.name + '.app')
 
@@ -154,5 +121,7 @@ function buildMacApp (opts, cb, newApp) {
         cb(err, appPath)
       })
     }
+
+    common.prune(opts, paths.app, cb, moveApp)
   })
 }
diff --git a/win32.js b/win32.js
index be3a5eb..bc3eb81 100644
--- a/win32.js
+++ b/win32.js
@@ -1,13 +1,12 @@
 var os = require('os')
 var path = require('path')
-var child = require('child_process')
 
 var mkdirp = require('mkdirp')
 var rimraf = require('rimraf')
 var ncp = require('ncp').ncp
-var asar = require('asar')
 var mv = require('mv')
 var rcedit = require('rcedit')
+var common = require('./common')
 
 module.exports = {
   createApp: function createApp (opts, electronApp, cb) {
@@ -50,44 +49,18 @@ function buildWinApp (opts, cb, newApp) {
     app: path.join(newApp, 'resources', 'app')
   }
 
-  function filter (file) {
-    // convert slashes so unix-format ignores work
-    file = file.replace(/\\/g, '/')
-
-    var ignore = opts.ignore || []
-    if (!Array.isArray(ignore)) ignore = [ignore]
-    for (var i = 0; i < ignore.length; i++) {
-      if (file.match(ignore[i])) {
-        return false
-      }
-    }
-    return true
-  }
-
-  // copy users app into .app
-  ncp(opts.dir, paths.app, {filter: filter, dereference: true}, function copied (err) {
+  // copy users app into destination path
+  ncp(opts.dir, paths.app, {filter: common.userIgnoreFilter(opts, true), dereference: true}, function copied (err) {
     if (err) return cb(err)
 
-    if (opts.prune) {
-      prune(function pruned (err) {
-        if (err) return cb(err)
-        moveApp()
-      })
-    } else {
-      moveApp()
-    }
-
-    function prune (cb) {
-      child.exec('npm prune --production', { cwd: paths.app }, cb)
-    }
-
     function moveApp () {
       // finally, move app into cwd
       var finalPath = path.join(opts.out || process.cwd(), opts.name + '-win32')
       copy(newApp, finalPath, function moved (err) {
         if (err) return cb(err)
         if (opts.asar) {
-          asarApp(function (err) {
+          var finalPath = path.join(opts.out || process.cwd(), opts.name + '-win32', 'resources')
+          common.asarApp(finalPath, function (err) {
             if (err) return cb(err)
             updateIcon()
           })
@@ -109,17 +82,8 @@ function buildWinApp (opts, cb, newApp) {
       rcedit(exePath, {icon: opts.icon}, function (err) {
         cb(err, finalPath)
       })
-
     }
 
-    function asarApp (cb) {
-      var finalPath = path.join(opts.out || process.cwd(), opts.name + '-win32', 'resources')
-      var src = path.join(finalPath, 'app')
-      var dest = path.join(finalPath, 'app.asar')
-      asar.createPackage(src, dest, function (err) {
-        if (err) return cb(err)
-        rimraf(src, cb)
-      })
-    }
+    common.prune(opts, paths.app, cb, moveApp)
   })
 }