diff --git a/src/core/manager.c b/src/core/manager.c
index cff38e28de..8b818bec91 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -2319,7 +2319,10 @@ int manager_load_unit_from_dbus_path(Manager *m, const char *s, sd_bus_error *e,
                 return sd_bus_error_setf(e, BUS_ERROR_NO_UNIT_FOR_INVOCATION_ID, "No unit with the specified invocation ID " SD_ID128_FORMAT_STR " known.", SD_ID128_FORMAT_VAL(invocation_id));
         }
 
-        /* If this didn't work, we use the suffix as unit name. */
+        /* If this didn't work, we check if this is a unit name */
+        if (!unit_name_is_valid(n, UNIT_NAME_PLAIN|UNIT_NAME_INSTANCE))
+                return sd_bus_error_setf(e, SD_BUS_ERROR_INVALID_ARGS, "Unit name %s is neither a valid invocation ID nor unit name.", n);
+
         r = manager_load_unit(m, n, NULL, e, &u);
         if (r < 0)
                 return r;
diff --git a/src/libsystemd/sd-bus/bus-objects.c b/src/libsystemd/sd-bus/bus-objects.c
index b6f5afe1b3..98911d5203 100644
--- a/src/libsystemd/sd-bus/bus-objects.c
+++ b/src/libsystemd/sd-bus/bus-objects.c
@@ -974,8 +974,10 @@ static int process_introspect(
                 /* Nothing?, let's see if we exist at all, and if not
                  * refuse to do anything */
                 r = bus_node_exists(bus, n, m->path, require_fallback);
-                if (r <= 0)
+                if (r <= 0) {
+                        r = bus_maybe_reply_error(m, r, &error);
                         goto finish;
+                }
                 if (bus->nodes_modified) {
                         r = 0;
                         goto finish;
@@ -1199,7 +1201,7 @@ static int process_get_managed_objects(
 
         r = get_child_nodes(bus, m->path, n, CHILDREN_RECURSIVE, &s, &error);
         if (r < 0)
-                return r;
+                return bus_maybe_reply_error(m, r, &error);
         if (bus->nodes_modified)
                 return 0;
 
@@ -1214,7 +1216,7 @@ static int process_get_managed_objects(
         SET_FOREACH(path, s, i) {
                 r = object_manager_serialize_path_and_fallbacks(bus, reply, path, &error);
                 if (r < 0)
-                        return r;
+                        return bus_maybe_reply_error(m, r, &error);
 
                 if (bus->nodes_modified)
                         return 0;
@@ -1344,7 +1346,7 @@ static int object_find_and_run(
         if (!*found_object) {
                 r = bus_node_exists(bus, n, m->path, require_fallback);
                 if (r < 0)
-                        return r;
+                        return bus_maybe_reply_error(m, r, NULL);
                 if (bus->nodes_modified)
                         return 0;
                 if (r > 0)