diff --git a/akka-cluster/src/main/resources/reference.conf b/akka-cluster/src/main/resources/reference.conf
index 8c905d5b29..cdaf8c729c 100644
--- a/akka-cluster/src/main/resources/reference.conf
+++ b/akka-cluster/src/main/resources/reference.conf
@@ -33,7 +33,6 @@ akka {
     # how often should the node move nodes, marked as unreachable by the failure detector, out of the membership ring?
     unreachable-nodes-reaper-interval = 1s
 
-    # accrual failure detection config
     failure-detector {
 
       # defines the failure detector threshold
@@ -43,6 +42,8 @@ akka {
       #     actual crashes
       threshold = 8
 
+      implementation-class = ""
+
       max-sample-size = 1000
     }
   }