diff --git a/quamash/_windows.py b/quamash/_windows.py
index c94ef46..73e4aa4 100644
--- a/quamash/_windows.py
+++ b/quamash/_windows.py
@@ -40,8 +40,10 @@ def _process_events(self, events):
 			try:
 				self._logger.debug('Invoking event callback {}'.format(callback))
 				value = callback(transferred, key, ov)
-			except OSError:
-				self._logger.warning('Event callback failed', exc_info=sys.exc_info())
+			except OSError as e:
+				self._logger.debug('Event callback failed', exc_info=sys.exc_info())
+				if not f.done():
+					f.set_exception(e)
 			else:
 				f.set_result(value)