--- a/python/mozboot/mozboot/archlinux.py
+++ b/python/mozboot/mozboot/archlinux.py
@@ -163,18 +163,18 @@ class ArchlinuxBootstrapper(BaseBootstra
 
         self.run_as_root(command)
 
     def pacman_update(self):
         command = ['pacman', '-S', '--refresh']
 
         self.run_as_root(command)
 
-    def run(self, command):
-        subprocess.check_call(command, stdin=sys.stdin)
+    def run(self, command, env=None):
+        subprocess.check_call(command, stdin=sys.stdin, env=env)
 
     def download(self, uri):
         command = ['curl', '-L', '-O', uri]
         self.run(command)
 
     def unpack(self, path, name, ext):
         if ext == 'gz':
             compression = '-z'
@@ -184,18 +184,20 @@ class ArchlinuxBootstrapper(BaseBootstra
             compression == 'x'
 
         name = os.path.join(path, name) + '.tar.' + ext
         command = ['tar', '-x', compression, '-f', name, '-C', path]
         self.run(command)
 
     def makepkg(self, name):
         command = ['makepkg', '-s']
-        self.run(command)
-        pack = glob.glob(name + '*.tar.xz')[0]
+        makepkg_env = os.environ.copy()
+        makepkg_env['PKGEXT'] = '.pkg.tar.xz'
+        self.run(command, env=makepkg_env)
+        pack = glob.glob(name + '*.pkg.tar.xz')[0]
         command = ['pacman', '-U']
         if self.no_interactive:
             command.append('--noconfirm')
         command.append(pack)
         self.run_as_root(command)
 
     def aur_install(self, *packages):
         path = tempfile.mkdtemp()