diff --git a/lib/ctblsolv.gi b/lib/ctblsolv.gi
index 8ef4d34b62..05d2c8be80 100644
--- a/lib/ctblsolv.gi
+++ b/lib/ctblsolv.gi
@@ -630,7 +630,8 @@ InstallGlobalFunction( CoveringTriplesCharacters, function( G, z )
       k:= KernelUnderDualAction( O, Opcgs,
               CanonicalRepresentativeOfExternalSet( orb ) );
       if not zn in k then
-        t:= SubgroupNC( G, StabilizerOfExternalSet( orb ) );
+        t:= StabilizerOfExternalSet( orb );
+        Assert( 1, IsIdenticalObj( Parent( t ), G ) );
         h:= NaturalHomomorphismByNormalSubgroupNC( t, k );
         img:= ImagesSource( h );
         Append( r,
diff --git a/tst/testbugfix/2019-11-28-IrrConlon.tst b/tst/testbugfix/2019-11-28-IrrConlon.tst
new file mode 100644
index 0000000000..c8013542bb
--- /dev/null
+++ b/tst/testbugfix/2019-11-28-IrrConlon.tst
@@ -0,0 +1,4 @@
+# the following used to run into an error
+# reported by Benjamin Sambale
+gap> Length(IrrConlon(SmallGroup(8,2)));
+8