diff --git a/image_creator/os_type/windows/vm.py b/image_creator/os_type/windows/vm.py
index 4501166ca963c20dc160791bb5c284e42e326f5b..024d19f78241468ca0c20c1fac9ac601dc134cd7 100644
--- a/image_creator/os_type/windows/vm.py
+++ b/image_creator/os_type/windows/vm.py
@@ -116,8 +116,7 @@ class VM(object):
         if 'mem' in self.params:
             args.extend(['-m', str(self.params['mem'].value)])
 
-        args.extend(['-drive',
-                     'file=%s,format=raw,cache=unsafe,if=%s' %
+        args.extend(['-drive', 'file=%s,cache=unsafe,if=%s' %
                      (self.disk, self.interface)])
 
         args.extend(