diff --git a/src/calibre/utils/ipc/pool.py b/src/calibre/utils/ipc/pool.py
index dfc3b9bfe0..624081d58a 100644
--- a/src/calibre/utils/ipc/pool.py
+++ b/src/calibre/utils/ipc/pool.py
@@ -101,20 +101,9 @@ class Pool(Thread):
         jobs. Can raise the :class:`Failure` exception is data could not be
         sent to workers.'''
         with self.lock:
-            self.common_data = cPickle.dumps(data, -1)
-            if len(self.common_data) > MAX_SIZE:
-                self.cd_file = PersistentTemporaryFile('pool_common_data')
-                with self.cd_file as f:
-                    f.write(self.common_data)
-                self.common_data = cPickle.dumps(File(f.name), -1)
-            for worker in self.available_workers:
-                try:
-                    worker.set_common_data(self.common_data)
-                except Exception:
-                    import traceback
-                    self.terminal_failure = TerminalFailure('Worker process crashed while sending common data', traceback.format_exc())
-                    self.terminal_error()
-                    raise Failure(self.terminal_failure)
+            if self.failed:
+                raise Failure(self.terminal_failure)
+            self.events.put(data)
 
     def start_worker(self):
         try:
@@ -154,7 +143,7 @@ class Pool(Thread):
                 if self.start_worker() is False:
                     return False
             return self.run_job(job)
-        else:
+        elif isinstance(event, WorkerResult):
             worker_result = event
             self.busy_workers.pop(worker_result.worker, None)
             self.available_workers.append(worker_result.worker)
@@ -164,6 +153,21 @@ class Pool(Thread):
                 self.terminal_error()
                 return False
             self.results.put(worker_result)
+        else:
+            self.common_data = cPickle.dumps(event, -1)
+            if len(self.common_data) > MAX_SIZE:
+                self.cd_file = PersistentTemporaryFile('pool_common_data')
+                with self.cd_file as f:
+                    f.write(self.common_data)
+                self.common_data = cPickle.dumps(File(f.name), -1)
+            for worker in self.available_workers:
+                try:
+                    worker.set_common_data(self.common_data)
+                except Exception:
+                    import traceback
+                    self.terminal_failure = TerminalFailure('Worker process crashed while sending common data', traceback.format_exc())
+                    self.terminal_error()
+                    return False
 
         while self.pending_jobs and self.available_workers:
             if self.run_job(self.pending_jobs.pop()) is False: