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 85ee7621..f3f898bb 100644
--- a/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java
+++ b/src/java/com/threerings/media/tile/bundle/tools/DirectoryTileSetBundler.java
@@ -87,25 +87,28 @@ public class DirectoryTileSetBundler extends TileSetBundler
 
                     try {
                         // create a trimmed object tileset, which will
-                        // write the trimmed tileset image to the destination
-                        // output stream
+                        // write the trimmed tileset image to the destination output stream
                         File outFile = new File(target, imagePath);
+                        FileOutputStream fout = null;
+                        
                         if (outFile.lastModified() > newestMod) {
                             // Our file's newer than the newest bundle mod - up to date.
+                            // So don't actually do anything
                             
-                            // FIXME: We can't just skip it, since we would've normally trimmed it,
-                            // so we need to get an appropriate TrimmedObjectTileSet added to our
-                            // bundle in place of this old ObjectTileSet.
-                            //continue;
+                            // TODO: Ideally, we'd like to skip re-trimming altogether, since that's
+                            // expensive, but for the moment, we're at least doing half as much by
+                            // not writing out the trimmed image.
+                            
+                        } else {
+                            // It's changed, so let's open the file & do all that jazz
+                            outFile.getParentFile().mkdirs();
+                            fout = new FileOutputStream(outFile);
                         }
-                        outFile.getParentFile().mkdirs();
-                        FileOutputStream fout = new FileOutputStream(outFile);
+                        
                         TrimmedObjectTileSet tset =
-                            TrimmedObjectTileSet.trimObjectTileSet(
-                                (ObjectTileSet)set, fout, "png");
+                            TrimmedObjectTileSet.trimObjectTileSet((ObjectTileSet)set, fout, "png");
                         tset.setImagePath(imagePath);
-                        // replace the original set with the trimmed
-                        // tileset in the tileset bundle
+                        // replace the original set with the trimmed tileset in the tileset bundle
                         bundle.addTileSet(tileSetId, tset);
 
                     } catch (Exception e) {
diff --git a/src/java/com/threerings/media/tile/util/TileSetTrimmer.java b/src/java/com/threerings/media/tile/util/TileSetTrimmer.java
index b4d84648..1546c8f8 100644
--- a/src/java/com/threerings/media/tile/util/TileSetTrimmer.java
+++ b/src/java/com/threerings/media/tile/util/TileSetTrimmer.java
@@ -151,11 +151,13 @@ public class TileSetTrimmer
             xoff += tb.width;
         }
 
-        // write out trimmed image
-        if (imgFormat == null || FastImageIO.FILE_SUFFIX.equals(imgFormat)) {
-            FastImageIO.write(image, destImage);
-        } else {
-            ImageIO.write(image, imgFormat, destImage);
+        if (destImage != null) {
+            // write out trimmed image
+            if (imgFormat == null || FastImageIO.FILE_SUFFIX.equals(imgFormat)) {
+                FastImageIO.write(image, destImage);
+            } else {
+                ImageIO.write(image, imgFormat, destImage);
+            }
         }
     }
 }