diff --git a/src/mol-plugin-ui/sequence.tsx b/src/mol-plugin-ui/sequence.tsx
index 56f6facfee257f7b28507ee0a47c8c77cb5aecd7..6913181b4735e31cad784f1a4d50e20710387767 100644
--- a/src/mol-plugin-ui/sequence.tsx
+++ b/src/mol-plugin-ui/sequence.tsx
@@ -383,10 +383,10 @@ export class SequenceView extends PluginUIComponent<{ defaultMode?: SequenceView
 
                     if (values.mode === 'single') return elem;
 
-                    return <>
+                    return <React.Fragment key={i}>
                         <div className='msp-sequence-chain-label'>{s.label}</div>
                         {elem}
-                    </>;
+                    </React.Fragment>;
                 })}
             </NonEmptySequenceWrapper>
         </div>;