diff --git a/unix/x0vncserver/PollingManager.h b/unix/x0vncserver/PollingManager.h
index 27bbf0f..b26e643 100644
--- a/unix/x0vncserver/PollingManager.h
+++ b/unix/x0vncserver/PollingManager.h
@@ -106,6 +106,9 @@
   // Check neighboring tiles and update pmxChanged[] matrix.
   void checkNeighbors(bool *pChangeFlags);
 
+  // DEBUG: Print the list of changed tiles.
+  void printChanges(const char *header, const bool *pChangeFlags);
+
   // Video detection functions.
   void detectVideo();
   void getVideoAreaRect(Rect *result);