diff --git a/packages/block-library/src/search/index.php b/packages/block-library/src/search/index.php
index 87e12f5d33d079..50c436270d4caa 100644
--- a/packages/block-library/src/search/index.php
+++ b/packages/block-library/src/search/index.php
@@ -152,17 +152,22 @@ function render_block_core_search( $attributes ) {
 		}
 	}
 
-	$field_markup_classes = $is_button_inside ? $border_color_classes : '';
-	$field_markup         = sprintf(
-		'<div class="wp-block-search__inside-wrapper %s" %s>%s</div>',
-		esc_attr( $field_markup_classes ),
+	$field_markup_classes = array(
+		'wp-block-search__inside-wrapper',
+	);
+	if ( $is_button_inside && ! empty( $border_color_classes ) ) {
+		$field_markup_classes[] = $border_color_classes;
+	}
+	$field_markup       = sprintf(
+		'<div class="%s" %s>%s</div>',
+		esc_attr( implode( ' ', $field_markup_classes ) ),
 		$inline_styles['wrapper'],
 		$input . $query_params_markup . $button
 	);
-	$wrapper_attributes   = get_block_wrapper_attributes(
+	$wrapper_attributes = get_block_wrapper_attributes(
 		array( 'class' => $classnames )
 	);
-	$form_directives      = '';
+	$form_directives    = '';
 
 	// If it's interactive, add the directives.
 	if ( $is_expandable_searchfield ) {