diff --git a/typescript/packages/common-html/src/render.ts b/typescript/packages/common-html/src/render.ts
index ae23ecaef..e52d2ae5a 100644
--- a/typescript/packages/common-html/src/render.ts
+++ b/typescript/packages/common-html/src/render.ts
@@ -248,7 +248,7 @@ const cleanEventProp = (key: string) => {
   if (!key.startsWith("on")) {
     return null;
   }
-  return key.slice(2);
+  return key.slice(2).toLowerCase();
 };
 
 /** Attach an event listener, returning a function to cancel the listener */