diff --git a/unix/x0vncserver/PollingManager.cxx b/unix/x0vncserver/PollingManager.cxx
index 81624a9..a1534d9 100644
--- a/unix/x0vncserver/PollingManager.cxx
+++ b/unix/x0vncserver/PollingManager.cxx
@@ -255,7 +255,7 @@
   return nTilesChanged;
 }
 
-int PollingManager::sendChanges(VNCServer *server)
+int PollingManager::sendChanges(VNCServer *server) const
 {
   const bool *pChangeFlags = m_changeFlags;
   int nTilesChanged = 0;