Index: sys/geom/virstor/g_virstor.c
===================================================================
--- sys/geom/virstor/g_virstor.c	(revision 239019)
+++ sys/geom/virstor/g_virstor.c	(working copy)
@@ -234,6 +234,12 @@
 			return;
 		}
 		sc = virstor_find_geom(cp, name);
+		if (sc == NULL) {
+			gctl_error(req, "Don't know anything about '%s'", name);
+			g_topology_unlock();
+			return;
+		}
+
 		LOG_MSG(LVL_INFO, "Stopping %s by the userland command",
 		    sc->geom->name);
 		update_metadata(sc);