diff --git a/lib/keywords/requireAllExcept.js b/lib/keywords/requireAllExcept.js
index 9f3135a..c015c02 100644
--- a/lib/keywords/requireAllExcept.js
+++ b/lib/keywords/requireAllExcept.js
@@ -12,7 +12,7 @@ const compile = async (schema, _ast, parentSchema) => {
   const propertyNames = Browser.typeOf(propertiesSchema) === "object" ? Browser.keys(propertiesSchema) : [];
 
   const required = new Set(propertyNames);
-  requireAllExcept.forEach((propertyName) => propertyNames.remove(propertyName));
+  requireAllExcept.forEach((propertyName) => required.delete(propertyName));
   return [...required];
 };