diff --git a/src/java/com/threerings/resource/KnownAvailabilityResourceBundle.java b/src/java/com/threerings/resource/KnownAvailabilityResourceBundle.java
new file mode 100644
index 00000000..863aeea0
--- /dev/null
+++ b/src/java/com/threerings/resource/KnownAvailabilityResourceBundle.java
@@ -0,0 +1,27 @@
+package com.threerings.resource;
+
+import java.util.Set;
+
+/**
+ * Keeps a set of known resources and allows implementors to ask if a resource is in it before
+ * performing a potentially expensive failed lookup.
+ */
+public abstract class KnownAvailabilityResourceBundle extends ResourceBundle
+{
+    public KnownAvailabilityResourceBundle (Set<String> availableResources)
+    {
+        _rsrcs = availableResources;
+    }
+
+    /**
+     * Returns whether we believe the path to be available. If we have no list, we assume
+     * everything may be available.
+     */
+    protected boolean isPossiblyAvailable (String path)
+    {
+        return _rsrcs == null || _rsrcs.contains(path);
+    }
+
+    /** All the resources included in this bundle. */
+    protected Set<String> _rsrcs;
+}
diff --git a/src/java/com/threerings/resource/NetworkResourceBundle.java b/src/java/com/threerings/resource/NetworkResourceBundle.java
index a0c7a37d..30ee2ce0 100644
--- a/src/java/com/threerings/resource/NetworkResourceBundle.java
+++ b/src/java/com/threerings/resource/NetworkResourceBundle.java
@@ -21,32 +21,25 @@
 
 package com.threerings.resource;
 
+import static com.threerings.resource.Log.log;
+
+import java.awt.image.BufferedImage;
+import java.io.IOException;
+import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
 import java.security.AccessControlException;
-
-import java.util.HashSet;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-import java.awt.image.BufferedImage;
-
-import static com.threerings.resource.Log.log;
+import java.util.Set;
 
 /**
  * Resource bundle that retrieves its contents via HTTP over the network from a root URL.
  */
-public class NetworkResourceBundle extends ResourceBundle
+public class NetworkResourceBundle extends KnownAvailabilityResourceBundle
 {
-    public NetworkResourceBundle (String root, String path)
-    {
-        this(root, path, null);
-    }
-
-    public NetworkResourceBundle (String root, String path, HashSet<String> rsrcList)
+    public NetworkResourceBundle (String root, String path, Set<String> rsrcList)
     {
+        super(rsrcList);
         if (!root.endsWith("/")) {
             root += "/";
         }
@@ -56,8 +49,6 @@ public class NetworkResourceBundle extends ResourceBundle
             log.warning("Created malformed URL for resource. [root=" + root + ", path=" + path);
         }
         _ident = path;
-
-        _rsrcList = rsrcList;
     }
 
     @Override // documentation inherited
@@ -71,7 +62,7 @@ public class NetworkResourceBundle extends ResourceBundle
         throws IOException
     {
         // If we can reject it before opening a connection, then save the network latency.
-        if (!inResourceList(path)) {
+        if (!isPossiblyAvailable(_ident + path)) {
             return null;
         }
 
@@ -81,14 +72,11 @@ public class NetworkResourceBundle extends ResourceBundle
 
     protected static InputStream getResource(URL resourceUrl)
     {
-        URLConnection ucon = null;
+        URLConnection ucon;
         try {
             ucon = resourceUrl.openConnection();
         } catch (IOException ioe) {
             log.warning("Unable to open connection [url=" + resourceUrl + ", ex=" + ioe + "]");
-        }
-
-        if (ucon == null) {
             return null;
         }
 
@@ -115,15 +103,6 @@ public class NetworkResourceBundle extends ResourceBundle
         return ResourceManager.loadImage(in, false);
     }
 
-    /**
-     * Returns whether we believe the path to be available.  If we have no list, we assume
-     *  everything may be available.
-     */
-    protected boolean inResourceList (String path)
-    {
-        return _rsrcList == null || _rsrcList.contains(_ident + path);
-    }
-
     /**
      * Returns a string representation of this resource bundle.
      */
@@ -138,7 +117,4 @@ public class NetworkResourceBundle extends ResourceBundle
 
     /** Our root url to the resources in this bundle. */
     protected URL _bundleURL;
-
-    /** A list of all the resources included in this bundle. */
-    protected HashSet<String> _rsrcList;
 }
diff --git a/src/java/com/threerings/resource/ResourceManager.java b/src/java/com/threerings/resource/ResourceManager.java
index 1fb0aab1..eff4d872 100644
--- a/src/java/com/threerings/resource/ResourceManager.java
+++ b/src/java/com/threerings/resource/ResourceManager.java
@@ -32,6 +32,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.Set;
 import java.util.StringTokenizer;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -852,7 +853,7 @@ public class ResourceManager
      * Creates an appropriate bundle for fetching resources from the network.
      */
     protected ResourceBundle createNetworkResourceBundle (String root, String path,
-        HashSet<String> rsrcList)
+        Set<String> rsrcList)
     {
         return new NetworkResourceBundle(root, path, rsrcList);
     }