diff --git a/packages/block-library/src/template-part/edit/use-template-part-post.js b/packages/block-library/src/template-part/edit/use-template-part-post.js
index 7ef0f705da2dc9..73e027f27eb364 100644
--- a/packages/block-library/src/template-part/edit/use-template-part-post.js
+++ b/packages/block-library/src/template-part/edit/use-template-part-post.js
@@ -2,6 +2,7 @@
  * WordPress dependencies
  */
 import { useSelect } from '@wordpress/data';
+import { cleanForSlug } from '@wordpress/url';
 
 export default function useTemplatePartPost( postId, slug, theme ) {
 	return useSelect(
@@ -22,18 +23,19 @@ export default function useTemplatePartPost( postId, slug, theme ) {
 			// load the auto-draft created from the
 			// relevant file.
 			if ( slug && theme ) {
+				const cleanedSlug = cleanForSlug( slug );
 				const posts = select( 'core' ).getEntityRecords(
 					'postType',
 					'wp_template_part',
 					{
 						status: [ 'publish', 'auto-draft' ],
-						slug,
+						slug: cleanedSlug,
 						theme,
 					}
 				);
 				const foundPosts = posts?.filter(
 					( post ) =>
-						post.slug === slug &&
+						post.slug === cleanedSlug &&
 						post.meta &&
 						post.meta.theme === theme
 				);