diff --git a/fhem/FHEM/TcpServerUtils.pm b/fhem/FHEM/TcpServerUtils.pm
index ae8e7b0bb..b954d2743 100644
--- a/fhem/FHEM/TcpServerUtils.pm
+++ b/fhem/FHEM/TcpServerUtils.pm
@@ -213,8 +213,12 @@ TcpServer_Close($@)
     delete($hash->{CD}); 
     delete($selectlist{$name});
     delete($hash->{FD});  # Avoid Read->Close->Write
-    delete $attr{$name} if($dodel);
-    delete $defs{$name} if($dodel);
+    if($dodel) {
+      delete $attr{$name};
+      delete $defs{$name};
+    } else {
+      $hash->{stacktrace} = stacktraceAsString(1);
+    }
   }
   if(defined($hash->{SERVERSOCKET})) {          # Server
     close($hash->{SERVERSOCKET});
@@ -243,6 +247,7 @@ TcpServer_Disown($)
     delete($hash->{CD});
     delete($selectlist{$name});
     delete($hash->{FD});  # Avoid Read->Close->Write
+    $hash->{stacktrace} = stacktraceAsString(1);
   }
 
   return;
diff --git a/fhem/fhem.pl b/fhem/fhem.pl
index 7647f7896..2baaaca2a 100755
--- a/fhem/fhem.pl
+++ b/fhem/fhem.pl
@@ -5365,6 +5365,14 @@ addToWritebuffer($$@)
 {
   my ($hash, $txt, $callback, $nolimit) = @_;
 
+  if(!defined($hash->{FD})) {
+    my $n = $hash->{NAME};
+    Log 1, "ERROR: addToWritebuffer for $n without FD";
+    Log 1, "probably caused at ".$hash->{stacktrace} if($hash->{stacktrace});
+    delete($defs{$n});
+    delete($attr{$n});
+    return;
+  }
   if($hash->{isChild}) {  # Wont go to the main select in a forked process
     TcpServer_WriteBlocking( $hash, $txt );
     if($callback) {