diff --git a/packages/block-editor/src/components/rich-text/format-toolbar/index.js b/packages/block-editor/src/components/rich-text/format-toolbar/index.js
index 42fa804f9297f..a02fce20d6fbe 100644
--- a/packages/block-editor/src/components/rich-text/format-toolbar/index.js
+++ b/packages/block-editor/src/components/rich-text/format-toolbar/index.js
@@ -21,7 +21,7 @@ const POPOVER_PROPS = {
 const FormatToolbar = () => {
 	return (
 		<>
-			{ [ 'bold', 'italic', 'link' ].map( ( format ) => (
+			{ [ 'bold', 'italic', 'link', 'unknown' ].map( ( format ) => (
 				<Slot
 					name={ `RichText.ToolbarControls.${ format }` }
 					key={ format }
diff --git a/packages/format-library/src/unknown/index.js b/packages/format-library/src/unknown/index.js
index f96c115bbce08..68c6d099fcad1 100644
--- a/packages/format-library/src/unknown/index.js
+++ b/packages/format-library/src/unknown/index.js
@@ -31,6 +31,7 @@ export const unknown = {
 
 		return (
 			<RichTextToolbarButton
+				name="unknown"
 				icon={ help }
 				title={ title }
 				onClick={ onClick }