diff --git a/core/src/main/java/hudson/util/MaskingClassLoader.java b/core/src/main/java/hudson/util/MaskingClassLoader.java
index 2a25910de5aee8bda6634b4d6303cd52e237aa4c..3220d30a5c43479f2d5ee19e1844532b07753726 100644
--- a/core/src/main/java/hudson/util/MaskingClassLoader.java
+++ b/core/src/main/java/hudson/util/MaskingClassLoader.java
@@ -23,6 +23,7 @@
  */
 package hudson.util;
 
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -41,7 +42,9 @@ public class MaskingClassLoader extends ClassLoader {
     /**
      * Prefix of the packages that should be hidden.
      */
-    private List<String> masks;
+    private List<String> masksClasses;
+
+    private List<String> masksResources;
 
     public MaskingClassLoader(ClassLoader parent, String... masks) {
         this(parent, Arrays.asList(masks));
@@ -49,12 +52,20 @@ public class MaskingClassLoader extends ClassLoader {
 
     public MaskingClassLoader(ClassLoader parent, Collection<String> masks) {
         super(parent);
-        this.masks = new ArrayList<String>(masks);
+        this.masksClasses = new ArrayList<String>(masks);
+        this.masksResources = new ArrayList<String>();
+
+        /**
+         * The name of a resource is a '/'-separated path name
+         */
+        for (String mask : masks) {
+            masksResources.add(mask.replace(".","/"));
+        }
     }
 
     @Override
     protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
-        for (String mask : masks) {
+        for (String mask : masksClasses) {
             if(name.startsWith(mask))
                 throw new ClassNotFoundException();
         }
@@ -62,7 +73,20 @@ public class MaskingClassLoader extends ClassLoader {
         return super.loadClass(name, resolve);
     }
 
+    @Override
+    public synchronized URL getResource(String name) {
+        for (String mask : masksResources) {
+            if(name.startsWith(mask))
+                return null;
+        }
+
+        return super.getResource(name);
+    }
+
     public synchronized void add(String prefix) {
-        masks.add(prefix);
+        masksClasses.add(prefix);
+        if(prefix !=null){
+            masksResources.add(prefix.replace(".","/"));
+        }
     }
 }
diff --git a/test/src/test/java/hudson/ClassicPluginStrategyTest.java b/test/src/test/java/hudson/ClassicPluginStrategyTest.java
index 3080dd7028cb9d836c0d40cb9df995979023f7fe..8075984f168a01a5b65b3a8841757d902eae4501 100644
--- a/test/src/test/java/hudson/ClassicPluginStrategyTest.java
+++ b/test/src/test/java/hudson/ClassicPluginStrategyTest.java
@@ -1,19 +1,19 @@
 /*
  * The MIT License
- * 
+ *
  * Copyright (c) 2004-2010, Sun Microsystems, Inc., Kohsuke Kawaguchi,
  * Alan Harder
- * 
+ *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
- * 
+ *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
- * 
+ *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
@@ -26,6 +26,7 @@ package hudson;
 
 import org.jvnet.hudson.test.Issue;
 import org.jvnet.hudson.test.HudsonTestCase;
+import org.jvnet.hudson.test.LenientRunnable;
 import org.jvnet.hudson.test.recipes.LocalData;
 
 import java.net.URL;
@@ -87,4 +88,19 @@ public class ClassicPluginStrategyTest extends HudsonTestCase {
                 fail("disabled dependency should not be included");
         }
     }
+
+    /**
+     * Test finding resources under masking.
+     * "foo1" plugin contains attribute of Mask-Classes: org.apache.http.
+     */
+    @LocalData
+    @Issue("JENKINS-27289")
+    public void testMaskResourceClassLoader() throws Exception {
+        PluginWrapper pw = jenkins.getPluginManager().getPlugin("foo1");
+        Class<?> clazz = pw.classLoader.loadClass("org.apache.http.impl.io.SocketInputBuffer");
+        ClassLoader cl = clazz.getClassLoader();
+        URL url = cl.getResource("org/apache/http/impl/io/SocketInputBuffer.class");
+        assert url != null;
+        assertTrue("expected to find the class from foo1 plugin", url.toString().contains("plugins/foo1"));
+    }
 }
diff --git a/test/src/test/resources/hudson/ClassicPluginStrategyTest/testMaskResourceClassLoader.zip b/test/src/test/resources/hudson/ClassicPluginStrategyTest/testMaskResourceClassLoader.zip
new file mode 100644
index 0000000000000000000000000000000000000000..75913a1b42977fa73c4f1a5528986291fe313dca
Binary files /dev/null and b/test/src/test/resources/hudson/ClassicPluginStrategyTest/testMaskResourceClassLoader.zip differ