diff --git a/tbsetup/libvtop_test.pm.in b/tbsetup/libvtop_test.pm.in
index 497f4119ef4310b6d9723509bd8221f35fdab6fe..6d011cf665e66d3ecddc6ccb8ab1910351ee28ea 100755
--- a/tbsetup/libvtop_test.pm.in
+++ b/tbsetup/libvtop_test.pm.in
@@ -5934,8 +5934,10 @@ sub InterpLinksAux($)
 			$protolink->SetAttribute("link/lan", $lan);
 			$protolink->SetAttribute("switchpath", "$pathA")
 			    if (defined($pathA));
-			$virtifaceA->_vlanname($lan);
-			$virtifaceB->_vlanname($lan);
+			$virtifaceA->_vlanname($lan)
+			    if (defined($virtifaceA));
+			$virtifaceB->_vlanname($lan)
+			    if (defined($virtifaceB));
 		    }
 		    $protolink->SetType($vlan_type);
 		    $protolink->SetRole($vlan_role);