diff --git a/modules/libjar/zipwriter/src/nsDeflateConverter.cpp b/modules/libjar/zipwriter/src/nsDeflateConverter.cpp
index 42e1649045c..9975a8bccfa 100644
--- a/modules/libjar/zipwriter/src/nsDeflateConverter.cpp
+++ b/modules/libjar/zipwriter/src/nsDeflateConverter.cpp
@@ -206,12 +206,16 @@ NS_IMETHODIMP nsDeflateConverter::OnStopRequest(nsIRequest *aRequest,
 nsresult nsDeflateConverter::PushAvailableData(nsIRequest *aRequest,
                                                nsISupports *aContext)
 {
+    PRUint32 bytesToWrite = sizeof(mWriteBuffer) - mZstream.avail_out;
+    // We don't need to do anything if there isn't any data
+    if (bytesToWrite == 0)
+        return NS_OK;
+
     nsresult rv;
     nsCOMPtr<nsIStringInputStream> stream =
              do_CreateInstance("@mozilla.org/io/string-input-stream;1", &rv);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    PRUint32 bytesToWrite = ZIP_BUFLEN - mZstream.avail_out;
     stream->ShareData((char*)mWriteBuffer, bytesToWrite);
     rv = mListener->OnDataAvailable(aRequest, mContext, stream, mOffset,
                                     bytesToWrite);
diff --git a/modules/libjar/zipwriter/test/unit/data/test_bug446708/thumbs/st14-1.tiff b/modules/libjar/zipwriter/test/unit/data/test_bug446708/thumbs/st14-1.tiff
new file mode 100644
index 00000000000..6b046575804
Binary files /dev/null and b/modules/libjar/zipwriter/test/unit/data/test_bug446708/thumbs/st14-1.tiff differ
diff --git a/modules/libjar/zipwriter/test/unit/test_bug446708.js b/modules/libjar/zipwriter/test/unit/test_bug446708.js
new file mode 100644
index 00000000000..fb1ec59fc04
--- /dev/null
+++ b/modules/libjar/zipwriter/test/unit/test_bug446708.js
@@ -0,0 +1,52 @@
+function run_test() {
+  var testBundle = do_get_file("modules/libjar/zipwriter/test/unit/data/test_bug446708");
+
+  RecursivelyZipDirectory(testBundle);
+}
+
+// Add |file| to the zip. |path| is the current path for the file.
+function AddToZip(zipWriter, path, file)
+{
+  var currentPath = path + file.leafName;
+  
+  if (file.isDirectory()) {
+    currentPath += "/";
+  }
+  
+  // THIS IS WHERE THE ERROR OCCURS, FOR THE FILE "st14-1.tiff" IN "test_bug446708"
+  zipWriter.addEntryFile(currentPath, Ci.nsIZipWriter.COMPRESSION_DEFAULT, file, false);
+  
+  // if it's a dir, continue adding its contents recursively...
+  if (file.isDirectory()) {
+    var entries = file.QueryInterface(Components.interfaces.nsIFile).directoryEntries;
+    while (entries.hasMoreElements()) {
+      var entry = entries.getNext().QueryInterface(Components.interfaces.nsIFile);
+      AddToZip(zipWriter, currentPath, entry);
+    }
+  }
+  
+  // ...otherwise, we're done
+}
+
+function RecursivelyZipDirectory(bundle)
+{
+  // create directory service
+  var dirUtils = Components.classes["@mozilla.org/file/directory_service;1"]
+      .createInstance(Components.interfaces.nsIProperties);
+  
+  // get the temp dir, where our temporary zip attachments can be stored
+  var tempFile = dirUtils.get("TmpD", Components.interfaces.nsIFile).clone();
+
+  // create unique file there
+  tempFile.append(bundle.leafName + ".zip");
+  tempFile.createUnique(Components.interfaces.nsIFile.NORMAL_FILE_TYPE, 
+                        0600);
+  
+  zipW.open(tempFile, PR_RDWR | PR_CREATE_FILE | PR_TRUNCATE);
+  
+  AddToZip(zipW, "", bundle); 
+  
+  // we're done.
+  zipW.close();
+}
+