The following test reproduces this issue: (function() { "use strict" ; const dbName = "applyOpsReplicatedCreateIndexCrash" ; const collName = "coll" ; const rst = new ReplSetTest({nodes: 2}); rst.startSet(); rst.initiate(); const db = rst.getPrimary().getDB(dbName); const coll = db.getCollection(collName); db.coll.drop(); db.coll.insert({}); db.adminCommand({ applyOps: [{ op: 'c' , ns: coll.getFullName(), o: { createIndexes: coll.getName(), v: 2, background: {a: 1}, name: 'a_1_create_v2' , unknown: 1 } }] }); rst.stopSet(); })();