diff --git a/projects/ngx-datatable/src/lib/components/header/header-cell.component.ts b/projects/ngx-datatable/src/lib/components/header/header-cell.component.ts
index 9be783394..8ff0d2914 100644
--- a/projects/ngx-datatable/src/lib/components/header/header-cell.component.ts
+++ b/projects/ngx-datatable/src/lib/components/header/header-cell.component.ts
@@ -136,7 +136,7 @@ export class DataTableHeaderCellComponent implements OnInit {
         });
 
         if (typeof res === 'string') {
-          cls += res;
+          cls += ' ' + res;
         } else if (typeof res === 'object') {
           const keys = Object.keys(res);
           for (const k of keys) {