diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 9a56e399fcfecb..43ca8331534275 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -539,8 +539,8 @@ private static function get_responsive_container_markup( $attributes, $inner_blo
 			$inner_blocks_html,
 			$toggle_aria_label_open,
 			$toggle_aria_label_close,
-			esc_attr( implode( ' ', $responsive_container_classes ) ),
-			esc_attr( implode( ' ', $open_button_classes ) ),
+			esc_attr( trim( implode( ' ', $responsive_container_classes ) ) ),
+			esc_attr( trim( implode( ' ', $open_button_classes ) ) ),
 			( ! empty( $overlay_inline_styles ) ) ? "style=\"$overlay_inline_styles\"" : '',
 			$toggle_button_content,
 			$toggle_close_button_content,