diff --git a/src/java/com/threerings/cast/bundle/tools/ComponentBundlerTask.java b/src/java/com/threerings/cast/bundle/tools/ComponentBundlerTask.java
index fa79e055..92b092d1 100644
--- a/src/java/com/threerings/cast/bundle/tools/ComponentBundlerTask.java
+++ b/src/java/com/threerings/cast/bundle/tools/ComponentBundlerTask.java
@@ -302,16 +302,17 @@ public class ComponentBundlerTask extends Task
             DirectoryScanner ds = fs.getDirectoryScanner(getProject());
             File fromDir = fs.getDir(getProject());
             String[] srcFiles = ds.getIncludedFiles();
+            long tgtModificationDate = getTgtModificationDate(target);
             for (int f = 0; f < srcFiles.length; f++) {
                 File cfile = new File(fromDir, srcFiles[f]);
-                if (newer(cfile, target)) {
+                if (newer(cfile, tgtModificationDate)) {
                     return true;
                 }
             }
             return false;
 
         } else if (source instanceof File) {
-            return newer((File)source, target);
+            return newer((File)source, getTgtModificationDate(target));
 
         } else {
             System.err.println("Can't compare " + source +
@@ -324,9 +325,17 @@ public class ComponentBundlerTask extends Task
      * Returns true if <code>source</code> is newer than
      * <code>target</code>.
      */
-    protected boolean newer (File source, File target)
+    protected boolean newer (File source, long tgtModificationDate)
     {
-        return source.lastModified() > target.lastModified();
+        return source.lastModified() > tgtModificationDate;
+    }
+
+    /**
+     * Returns the last modified date of <code>target</code> to be compared for out-of-dateness.
+     */
+    protected long getTgtModificationDate (File target)
+    {
+        return target.lastModified();
     }
 
     /**
diff --git a/src/java/com/threerings/cast/bundle/tools/DirectoryComponentBundlerTask.java b/src/java/com/threerings/cast/bundle/tools/DirectoryComponentBundlerTask.java
index d3ab04e4..6318b09f 100644
--- a/src/java/com/threerings/cast/bundle/tools/DirectoryComponentBundlerTask.java
+++ b/src/java/com/threerings/cast/bundle/tools/DirectoryComponentBundlerTask.java
@@ -27,8 +27,9 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 
-import com.threerings.media.tile.TileSet;
+import com.threerings.util.FileUtil;
 
+import com.threerings.media.tile.TileSet;
 import com.threerings.media.tile.TrimmedTileSet;
 
 /**
@@ -62,9 +63,9 @@ public class DirectoryComponentBundlerTask extends ComponentBundlerTask
     }
 
     @Override // documentation inherited
-    protected boolean outOfDate (Object source, File target)
+    protected long getTgtModificationDate (File target)
     {
-        // Since we're updating individual files, assume always out of date and rebuild.
-        return true;
+        // Return the oldest modification date of anything within the directory.
+        return FileUtil.getOldestLastModified(target);
     }
  }
diff --git a/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java b/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java
index 507281b9..23c6f299 100644
--- a/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java
+++ b/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java
@@ -36,6 +36,7 @@ import javax.imageio.ImageIO;
 import org.apache.commons.io.IOUtils;
 
 import com.threerings.media.Log;
+import com.threerings.util.FileUtil;
 import com.threerings.media.tile.ImageProvider;
 import com.threerings.media.tile.ObjectTileSet;
 import com.threerings.media.tile.TileSet;
@@ -155,9 +156,9 @@ public class DirectoryTileSetBundler extends TileSetBundler
     }
 
     @Override // documentation inherited
-    protected boolean maySkipIfNewer ()
+    protected long getTgtModificationDate (File target)
     {
-        // Can't skip since we're copying individual files.
-        return false;
+        // Return the oldest modification date of anything within the directory.
+        return FileUtil.getOldestLastModified(target);
     }
 }
diff --git a/src/java/com/threerings/media/tile/bundle/tools/TileSetBundler.java b/src/java/com/threerings/media/tile/bundle/tools/TileSetBundler.java
index 2143c113..fe0ddaa2 100644
--- a/src/java/com/threerings/media/tile/bundle/tools/TileSetBundler.java
+++ b/src/java/com/threerings/media/tile/bundle/tools/TileSetBundler.java
@@ -310,7 +310,7 @@ public class TileSetBundler
         }
 
         // see if our newest file is newer than the tileset bundle
-        if (newest < target.lastModified() && maySkipIfNewer()) {
+        if (newest < getTgtModificationDate(target)) {
             return false;
         }
 
@@ -325,14 +325,6 @@ public class TileSetBundler
         return createBundle(target, bundle, improv, bundleDesc.getParent());
     }
 
-    /**
-     * Whether we're allowed to skip creation of the bundle if we're not out of date.
-     */
-    protected boolean maySkipIfNewer ()
-    {
-        return true;
-    }
-
     /**
      * Finish the creation of a tileset bundle jar file.
      *
@@ -462,6 +454,14 @@ public class TileSetBundler
         }
     }
 
+    /**
+     * Returns the last modified date of <code>target</code> to be compared for out-of-dateness.
+     */
+    protected long getTgtModificationDate (File target)
+    {
+        return target.lastModified();
+    }
+
     /** Replaces the image suffix with <code>.raw</code>. */
     protected static String adjustImagePath (String imagePath)
     {
diff --git a/src/java/com/threerings/util/FileUtil.java b/src/java/com/threerings/util/FileUtil.java
new file mode 100644
index 00000000..5db6e773
--- /dev/null
+++ b/src/java/com/threerings/util/FileUtil.java
@@ -0,0 +1,43 @@
+//
+// $Id$
+//
+// Nenya library - tools for developing networked games
+// Copyright (C) 2002-2007 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/nenya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.util;
+
+import java.io.File;
+
+public class FileUtil
+{
+    /**
+     * Returns the timestamp of the oldest modification date of any file within the directory.
+     */
+    public static long getOldestLastModified (File dir)
+    {
+        long oldest = dir.lastModified();
+        for (File file : dir.listFiles()) {
+            if (file.isDirectory()) {
+                oldest = Math.min(oldest, getOldestLastModified(file));
+            } else {
+                oldest = Math.min(oldest, file.lastModified());
+            }
+        }
+        return oldest;
+    }
+}