diff --git a/src/libnm-core-impl/nm-setting-ip-config.c b/src/libnm-core-impl/nm-setting-ip-config.c
index bdbd17aac..567cb73e5 100644
--- a/src/libnm-core-impl/nm-setting-ip-config.c
+++ b/src/libnm-core-impl/nm-setting-ip-config.c
@@ -5788,7 +5788,7 @@ _nm_sett_info_property_override_create_array_ip_config(int addr_family)
             .to_dbus_fcn   = _nm_setting_property_to_dbus_fcn_direct,
             .from_dbus_fcn = _nm_setting_property_from_dbus_fcn_direct_ip_config_gateway),
         .direct_offset = NM_STRUCT_OFFSET_ENSURE_TYPE(char *, NMSettingIPConfigPrivate, gateway),
-        .direct_set_string_ip_address_addr_family = addr_family);
+        .direct_set_string_ip_address_addr_family = addr_family + 1);
 
     _nm_properties_override_gobj(
         properties_override,
diff --git a/src/libnm-core-impl/nm-setting.c b/src/libnm-core-impl/nm-setting.c
index ccf80e971..2ae854c9d 100644
--- a/src/libnm-core-impl/nm-setting.c
+++ b/src/libnm-core-impl/nm-setting.c
@@ -668,7 +668,7 @@ _property_direct_set_string(const NMSettInfoProperty *property_info, char **dst,
     }
     if (property_info->direct_set_string_ip_address_addr_family != 0) {
         s = _nm_utils_ipaddr_canonical_or_invalid(
-            property_info->direct_set_string_ip_address_addr_family,
+            property_info->direct_set_string_ip_address_addr_family - 1,
             src);
         goto out_take;
     }
diff --git a/src/libnm-core-impl/tests/test-setting.c b/src/libnm-core-impl/tests/test-setting.c
index b4c67079e..8e804dadf 100644
--- a/src/libnm-core-impl/tests/test-setting.c
+++ b/src/libnm-core-impl/tests/test-setting.c
@@ -4585,6 +4585,13 @@ test_setting_metadata(void)
                                 + (!!sip->direct_set_string_ascii_strdown)
                                 + (sip->direct_set_string_ip_address_addr_family != 0);
 
+            G_STATIC_ASSERT_EXPR(AF_UNSPEC + 1 != 0);
+            g_assert(NM_IN_SET((int) sip->direct_set_string_ip_address_addr_family,
+                               0,
+                               AF_UNSPEC + 1,
+                               AF_INET + 1,
+                               AF_INET6 + 1));
+
             /* currently, we have no cases where special options are mixed. There is no problem to support
              * that, but as it's not needed, don't do it for now. */
             g_assert_cmpint(n_special_options, <=, 1);
diff --git a/src/libnm-core-intern/nm-core-internal.h b/src/libnm-core-intern/nm-core-internal.h
index f18f16cfd..429dc2b84 100644
--- a/src/libnm-core-intern/nm-core-internal.h
+++ b/src/libnm-core-intern/nm-core-internal.h
@@ -767,8 +767,10 @@ struct _NMSettInfoProperty {
      * MAC address length. */
     guint8 direct_set_string_mac_address_len : 5;
 
-    /* If non-zero, this is the addr-family (AF_INET/AF_INET6) for normalizing an IP
-     * address. */
+    /* If non-zero, this is the addr-family (AF_UNSPEC/AF_INET/AF_INET6) for normalizing an IP
+     * address. Note that AF_UNSPEC is zero, so to differentiate between zero and AF_UNSPEC
+     * this value is actually the address family + 1. So either zero or AF_UNSPEC+1, AF_INET+1,
+     * or AF_INET6+1. */
     guint8 direct_set_string_ip_address_addr_family : 5;
 
     /* Usually, properties that are set to the default value for the GParamSpec