diff --git a/packages/edit-site/src/components/global-styles/font-sizes/font-size.js b/packages/edit-site/src/components/global-styles/font-sizes/font-size.js
index 80b1ea55c405b..1ce4c97b91d98 100644
--- a/packages/edit-site/src/components/global-styles/font-sizes/font-size.js
+++ b/packages/edit-site/src/components/global-styles/font-sizes/font-size.js
@@ -46,6 +46,10 @@ function FontSize() {
 
 	const [ globalFluid ] = useGlobalSetting( 'typography.fluid' );
 
+	if ( ! origin || ! slug ) {
+		return;
+	}
+
 	// Get the font sizes from the origin, default to empty array.
 	const sizes = fontSizes[ origin ] ?? [];