diff --git a/commafeed-client/src/components/content/Content.tsx b/commafeed-client/src/components/content/Content.tsx
index e53412a2..492ad65c 100644
--- a/commafeed-client/src/components/content/Content.tsx
+++ b/commafeed-client/src/components/content/Content.tsx
@@ -80,7 +80,7 @@ class HighlightMatcher extends Matcher {
     }
 
     replaceWith(children: ChildrenNode): Node {
-        return <Mark>{children}</Mark>
+        return <Mark key={0}>{children}</Mark>
     }
 
     asTag(): string {