diff --git a/src/core/platform/nm-fake-platform.c b/src/core/platform/nm-fake-platform.c
index ebb6a795b9..7d8986d764 100644
--- a/src/core/platform/nm-fake-platform.c
+++ b/src/core/platform/nm-fake-platform.c
@@ -957,11 +957,10 @@ ipx_address_delete(NMPlatform   *platform,
     peer_addr_i = peer_addr ? *((guint32 *) peer_addr) : 0;
 
     nmp_cache_iter_for_each (&iter,
-                             nm_platform_lookup_object(platform,
-                                                       addr_family == AF_INET
-                                                           ? NMP_OBJECT_TYPE_IP4_ADDRESS
-                                                           : NMP_OBJECT_TYPE_IP6_ADDRESS,
-                                                       0),
+                             nm_platform_lookup_obj_type(platform,
+                                                         addr_family == AF_INET
+                                                             ? NMP_OBJECT_TYPE_IP4_ADDRESS
+                                                             : NMP_OBJECT_TYPE_IP6_ADDRESS),
                              &o) {
         const NMPObject *obj_old = NULL;
 
@@ -1139,7 +1138,7 @@ ip_route_add(NMPlatform              *platform,
         gboolean has_route_to_gw = FALSE;
 
         nmp_cache_iter_for_each (&iter,
-                                 nm_platform_lookup_object(platform, NMP_OBJECT_GET_TYPE(obj), 0),
+                                 nm_platform_lookup_obj_type(platform, NMP_OBJECT_GET_TYPE(obj)),
                                  &o) {
             if (addr_family == AF_INET) {
                 const NMPlatformIP4Route *item = NMP_OBJECT_CAST_IP4_ROUTE(o);
diff --git a/src/core/platform/tests/test-common.c b/src/core/platform/tests/test-common.c
index 24426a5414..9053d35173 100644
--- a/src/core/platform/tests/test-common.c
+++ b/src/core/platform/tests/test-common.c
@@ -102,7 +102,11 @@ nmtstp_platform_ip_address_find(NMPlatform *self, int ifindex, int addr_family,
     nm_assert_addr_family(addr_family);
     nm_assert(addr);
 
-    nmp_lookup_init_object(&lookup, NMP_OBJECT_TYPE_IP_ADDRESS(IS_IPv4), ifindex);
+    if (ifindex > 0)
+        nmp_lookup_init_object(&lookup, NMP_OBJECT_TYPE_IP_ADDRESS(IS_IPv4), ifindex);
+    else
+        nmp_lookup_init_obj_type(&lookup, NMP_OBJECT_TYPE_IP_ADDRESS(IS_IPv4));
+
     nm_platform_iter_obj_for_each (&iter, self, &lookup, &obj) {
         const NMPlatformIPAddress *a = NMP_OBJECT_CAST_IP_ADDRESS(obj);
 
diff --git a/src/libnm-platform/nmp-object.c b/src/libnm-platform/nmp-object.c
index 3154a23e80..8bd43ef0e5 100644
--- a/src/libnm-platform/nmp-object.c
+++ b/src/libnm-platform/nmp-object.c
@@ -2142,7 +2142,15 @@ nmp_lookup_init_object(NMPLookup *lookup, NMPObjectType obj_type, int ifindex)
                         NMP_OBJECT_TYPE_QDISC,
                         NMP_OBJECT_TYPE_TFILTER));
 
-    if (ifindex <= 0) {
+    if (G_UNLIKELY(
+            (ifindex < 0)
+            || (ifindex == 0
+                && !NM_IN_SET(obj_type, NMP_OBJECT_TYPE_IP4_ROUTE, NMP_OBJECT_TYPE_IP6_ROUTE)))) {
+        /* This function used to have a fallback that meant to lookup all objects, if
+         * ifindex is non-positive. As routes can have a zero ifindex, that fallback is
+         * confusing and no longer supported. Only have this code, to catch accidental bugs
+         * after the API change. */
+        nm_assert_not_reached();
         return nmp_lookup_init_obj_type(lookup, obj_type);
     }