diff --git a/fhem/FHEM/Blocking.pm b/fhem/FHEM/Blocking.pm
index 0f98b1a4f..3f25d3c1b 100644
--- a/fhem/FHEM/Blocking.pm
+++ b/fhem/FHEM/Blocking.pm
@@ -83,7 +83,7 @@ BlockingStart(;$)
 {
   my ($curr) = @_;
 
-  if($curr && $curr =~ m/^\d+$/) {
+  if($curr && $curr =~ m/^\d+$/ && $BC_hash{$curr}) {
     $BC_hash{$curr}{terminated} = 1;
     $curr = undef;
   }