diff --git a/core/src/main/java/hudson/DescriptorExtensionList.java b/core/src/main/java/hudson/DescriptorExtensionList.java
index 0856c686df462c47e9e253338830604363f7e493..3a570dc02309c0b3b9dcf4ebe2e7b9fed9cae4dd 100644
--- a/core/src/main/java/hudson/DescriptorExtensionList.java
+++ b/core/src/main/java/hudson/DescriptorExtensionList.java
@@ -29,12 +29,15 @@ import hudson.model.Hudson;
 import hudson.model.ViewDescriptor;
 import hudson.model.Descriptor.FormException;
 import hudson.util.Memoizer;
+import hudson.util.Iterators;
+import hudson.util.Iterators.FlattenIterator;
 import hudson.slaves.NodeDescriptor;
 import hudson.tasks.Publisher;
 import hudson.tasks.Publisher.DescriptorExtensionListImpl;
 
 import java.util.List;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.logging.Logger;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.lang.reflect.Type;
@@ -138,7 +141,7 @@ public class DescriptorExtensionList<T extends Describable<T>, D extends Descrip
     }
 
     /**
-     * Stores manually registered Descriptor instances.
+     * Stores manually registered Descriptor instances. Keyed by the {@link Describable} type.
      */
     private static final Memoizer<Class,CopyOnWriteArrayList> legacyDescriptors = new Memoizer<Class,CopyOnWriteArrayList>() {
         public CopyOnWriteArrayList compute(Class key) {
@@ -146,5 +149,20 @@ public class DescriptorExtensionList<T extends Describable<T>, D extends Descrip
         }
     };
 
+    /**
+     * List up all the legacy instances currently in use.
+     */
+    public static Iterable<Descriptor> listLegacyInstances() {
+        return new Iterable<Descriptor>() {
+            public Iterator<Descriptor> iterator() {
+                return new FlattenIterator<Descriptor,CopyOnWriteArrayList>(legacyDescriptors.values()) {
+                    protected Iterator expand(CopyOnWriteArrayList v) {
+                        return v.iterator();
+                    }
+                };
+            }
+        };
+    }
+
     private static final Logger LOGGER = Logger.getLogger(DescriptorExtensionList.class.getName());
 }
diff --git a/core/src/main/java/hudson/model/Hudson.java b/core/src/main/java/hudson/model/Hudson.java
index 6ba59691b573c205a27b4ffe631d0a80d20fe328..adcb5b6b04d08bc70e92de4a89e8bb62697ffe86 100644
--- a/core/src/main/java/hudson/model/Hudson.java
+++ b/core/src/main/java/hudson/model/Hudson.java
@@ -103,6 +103,7 @@ import hudson.util.HudsonIsRestarting;
 import hudson.util.DescribableList;
 import hudson.util.Futures;
 import hudson.util.Memoizer;
+import hudson.util.Iterators;
 import hudson.widgets.Widget;
 import net.sf.json.JSONObject;
 import org.acegisecurity.*;
@@ -691,7 +692,8 @@ public final class Hudson extends Node implements ItemGroup<TopLevelItem>, Stapl
      * this just doesn't scale.
      */
     public Descriptor getDescriptor(String fullyQualifiedClassName) {
-        for( Descriptor d : getExtensionList(Descriptor.class) )
+        // legacy descriptors that are reigstered manually doesn't show up in getExtensionList, so check them explicitly.
+        for( Descriptor d : Iterators.sequence(getExtensionList(Descriptor.class),DescriptorExtensionList.listLegacyInstances()) )
             if(d.clazz.getName().equals(fullyQualifiedClassName))
                 return d;
         return null;
diff --git a/core/src/main/java/hudson/tasks/BuildStep.java b/core/src/main/java/hudson/tasks/BuildStep.java
index 3fdb7b62c26f02bca906d0c451885ea8e5530b83..c893759df22bcffe1daf09103697960496124337 100644
--- a/core/src/main/java/hudson/tasks/BuildStep.java
+++ b/core/src/main/java/hudson/tasks/BuildStep.java
@@ -219,5 +219,10 @@ public interface BuildStep {
         public Iterator<Descriptor<Publisher>> iterator() {
             return core.iterator();
         }
+
+        @Override
+        public boolean remove(Object o) {
+            return core.remove(o);
+        }
     }
 }
diff --git a/core/src/main/java/hudson/util/DescriptorList.java b/core/src/main/java/hudson/util/DescriptorList.java
index a04ba4dcccf7756139dcc569f0582d594c88793a..e0a94d1970800f0dd24092efd8dbccae9682542a 100644
--- a/core/src/main/java/hudson/util/DescriptorList.java
+++ b/core/src/main/java/hudson/util/DescriptorList.java
@@ -130,6 +130,11 @@ public final class DescriptorList<T extends Describable<T>> extends AbstractList
         add(element); // order is ignored
     }
 
+    @Override
+    public boolean remove(Object o) {
+        return store().remove(o);
+    }
+
     /**
      * Gets the actual data store. This is the key to control the dual-mode nature of {@link DescriptorList}
      */
diff --git a/core/src/main/java/hudson/util/Memoizer.java b/core/src/main/java/hudson/util/Memoizer.java
index 3cb063ab7df659f66061761e17894c6718c75504..d150040906130569d79ab5b003b70d7f3d3489ae 100644
--- a/core/src/main/java/hudson/util/Memoizer.java
+++ b/core/src/main/java/hudson/util/Memoizer.java
@@ -65,4 +65,11 @@ public abstract class Memoizer<K,V> {
     public void clear() {
         store.clear();
     }
+
+    /**
+     * Provides a snapshot view of all {@code V}s.
+     */
+    public Iterable<V> values() {
+        return store.values();
+    }
 }
diff --git a/test/src/test/java/hudson/model/HudsonTest.java b/test/src/test/java/hudson/model/HudsonTest.java
index 26ce1a6b91c1cab497b0fe8ef6b2e72760f2ac8d..98d9d1e359ca6c879a08cdc4b3e1fc95857ecc3e 100644
--- a/test/src/test/java/hudson/model/HudsonTest.java
+++ b/test/src/test/java/hudson/model/HudsonTest.java
@@ -36,6 +36,7 @@ import hudson.search.SearchTest;
 import hudson.security.AuthorizationStrategy;
 import hudson.security.SecurityRealm;
 import hudson.tasks.Ant;
+import hudson.tasks.BuildStep;
 import hudson.tasks.Ant.AntInstallation;
 import hudson.tasks.Ant.DescriptorImpl;
 import org.jvnet.hudson.test.Email;
@@ -145,4 +146,22 @@ public class HudsonTest extends HudsonTestCase {
         // the master computer object should be still here
         wc.goTo("computer/(master)/");
     }
+
+    /**
+     * Legacy descriptors should be visible in the /descriptor/xyz URL.
+     */
+    @Email("http://www.nabble.com/1.286-version-and-description-The-requested-resource-%28%29-is-not--available.-td22233801.html")
+    public void testLegacyDescriptorLookup() throws Exception {
+        Descriptor dummy = new Descriptor(HudsonTest.class) {
+            public String getDisplayName() {
+                return "dummy";
+            }
+        };
+
+        BuildStep.PUBLISHERS.addRecorder(dummy);
+        assertSame(dummy,hudson.getDescriptor(HudsonTest.class.getName()));
+
+        BuildStep.PUBLISHERS.remove(dummy);
+        assertNull(hudson.getDescriptor(HudsonTest.class.getName()));
+    }
 }