diff --git a/src/settings/plugins/example/plugin.c b/src/settings/plugins/example/plugin.c
index 9f99a4f449..f7700297a5 100644
--- a/src/settings/plugins/example/plugin.c
+++ b/src/settings/plugins/example/plugin.c
@@ -569,7 +569,7 @@ get_unmanaged_specs (NMSystemConfigInterface *config)
 			}
 
 			specs = g_slist_append (specs, ids[i]);
-		} else if (!strncmp (ids[i], "interface-name:", 10) && nm_utils_iface_valid_name (ids[i] + 10)) {
+		} else if (!strncmp (ids[i], "interface-name:", 15) && nm_utils_iface_valid_name (ids[i] + 15)) {
 			specs = g_slist_append (specs, ids[i]);
 		} else {
 			g_warning ("Error in file '%s': invalid unmanaged-devices entry: '%s'", priv->conf_file, ids[i]);
diff --git a/src/settings/plugins/keyfile/plugin.c b/src/settings/plugins/keyfile/plugin.c
index 21ff114ff5..be3a48d032 100644
--- a/src/settings/plugins/keyfile/plugin.c
+++ b/src/settings/plugins/keyfile/plugin.c
@@ -466,7 +466,7 @@ get_unmanaged_specs (NMSystemConfigInterface *config)
 					p++;
 				}
 				specs = g_slist_append (specs, udis[i]);
-			} else if (!strncmp (udis[i], "interface-name:", 10) && nm_utils_iface_valid_name (udis[i] + 10)) {
+			} else if (!strncmp (udis[i], "interface-name:", 15) && nm_utils_iface_valid_name (udis[i] + 15)) {
 				specs = g_slist_append (specs, udis[i]);
 			} else {
 				g_warning ("Error in file '%s': invalid unmanaged-devices entry: '%s'", priv->conf_file, udis[i]);