diff --git a/test/src/main/java/org/jvnet/hudson/test/HudsonTestCase.java b/test/src/main/java/org/jvnet/hudson/test/HudsonTestCase.java
index 46586c999cf50bcb953dd4be874727291c457af6..04aa5daecf447b0b457943e27375a97ac5ea7180 100644
--- a/test/src/main/java/org/jvnet/hudson/test/HudsonTestCase.java
+++ b/test/src/main/java/org/jvnet/hudson/test/HudsonTestCase.java
@@ -461,6 +461,11 @@ public abstract class HudsonTestCase extends TestCase implements RootAction {
         context.setConfigurations(new Configuration[]{new WebXmlConfiguration(), new NoListenerConfiguration()});
         server.setHandler(context);
         context.setMimeTypes(MIME_TYPES);
+        if(Functions.isWindows()) {
+            // this is only needed on Windows because of the file
+            // locking issue as described in JENKINS-12647
+            context.setCopyWebDir(true);
+        }
 
         SocketConnector connector = new SocketConnector();
         connector.setHeaderBufferSize(12*1024); // use a bigger buffer as Stapler traces can get pretty large on deeply nested URL