--- a/eric6/DebugClients/Python/DebugClientBase.py	Mon Dec 07 19:52:49 2020 +0100
+++ b/eric6/DebugClients/Python/DebugClientBase.py	Mon Dec 07 19:53:15 2020 +0100
@@ -1212,6 +1212,9 @@
                 else:
                     # give up for too many errors
                     break
+            except ValueError:
+                # the client socket might already be closed, i.e. its fd is -1
+                break
             
             # reset the select error counter
             selectErrors = 0