diff --git a/.changeset/odd-books-share.md b/.changeset/odd-books-share.md
new file mode 100644
index 0000000000..858a2564ad
--- /dev/null
+++ b/.changeset/odd-books-share.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-backend': patch
+---
+
+Preserve default `allowedLocationTypes` when `setAllowedLocationTypes()` of `CatalogLocationsExtensionPoint` is not called.
diff --git a/plugins/catalog-backend/src/service/CatalogPlugin.ts b/plugins/catalog-backend/src/service/CatalogPlugin.ts
index 2f5fd9103d..269100e586 100644
--- a/plugins/catalog-backend/src/service/CatalogPlugin.ts
+++ b/plugins/catalog-backend/src/service/CatalogPlugin.ts
@@ -46,7 +46,7 @@ import { ForwardedError } from '@backstage/errors';
 class CatalogLocationsExtensionPointImpl
   implements CatalogLocationsExtensionPoint
 {
-  #locationTypes = new Array<string>();
+  #locationTypes: string[] | undefined;
 
   setAllowedLocationTypes(locationTypes: Array<string>) {
     this.#locationTypes = locationTypes;
@@ -293,9 +293,11 @@ export const catalogPlugin = createBackendPlugin({
         builder.addPermissionRules(...permissionExtensions.permissionRules);
         builder.setFieldFormatValidators(modelExtensions.fieldValidators);
 
-        builder.setAllowedLocationTypes(
-          locationTypeExtensions.allowedLocationTypes,
-        );
+        if (locationTypeExtensions.allowedLocationTypes) {
+          builder.setAllowedLocationTypes(
+            locationTypeExtensions.allowedLocationTypes,
+          );
+        }
 
         const { processingEngine, router } = await builder.build();