diff --git a/lib/compat/wordpress-6.6/class-gutenberg-rest-templates-controller-6-6.php b/lib/compat/wordpress-6.6/class-gutenberg-rest-templates-controller-6-6.php
index 4a25e06608235..525801cbb7f83 100644
--- a/lib/compat/wordpress-6.6/class-gutenberg-rest-templates-controller-6-6.php
+++ b/lib/compat/wordpress-6.6/class-gutenberg-rest-templates-controller-6-6.php
@@ -84,6 +84,10 @@ public function get_template_fallback( $request ) {
 			array_shift( $hierarchy );
 		} while ( ! empty( $hierarchy ) && empty( $fallback_template->content ) );
 
+		if ( ! $fallback_template ) {
+			return new WP_Error( 'rest_template_not_found', __( 'No fallback templates exist for that slug.', 'default' ), array( 'status' => 404 ) );
+		}
+
 		$response = $this->prepare_item_for_response( $fallback_template, $request );
 
 		return rest_ensure_response( $response );
diff --git a/packages/edit-post/src/store/selectors.js b/packages/edit-post/src/store/selectors.js
index 791b384d1e818..7c26950b27822 100644
--- a/packages/edit-post/src/store/selectors.js
+++ b/packages/edit-post/src/store/selectors.js
@@ -615,10 +615,13 @@ export const getEditedPostTemplate = createRegistrySelector(
 		const defaultTemplateId = select( coreStore ).getDefaultTemplateId( {
 			slug: slugToCheck,
 		} );
-		return select( coreStore ).getEditedEntityRecord(
-			'postType',
-			'wp_template',
-			defaultTemplateId
-		);
+
+		return defaultTemplateId
+			? select( coreStore ).getEditedEntityRecord(
+					'postType',
+					'wp_template',
+					defaultTemplateId
+			  )
+			: null;
 	}
 );