diff --git a/instrumentation/kamon-executors/src/main/resources/reference.conf b/instrumentation/kamon-executors/src/main/resources/reference.conf
index ad77b1907..dd344d8de 100644
--- a/instrumentation/kamon-executors/src/main/resources/reference.conf
+++ b/instrumentation/kamon-executors/src/main/resources/reference.conf
@@ -35,10 +35,8 @@ kanela.modules {
       "kanela.agent."
     ]
 
-    within = [
-      "scala.concurrent.ExecutionContext$",
-      "scala.concurrent.ExecutionContext$Implicits$"
-    ]
+    within += "scala.concurrent.ExecutionContext$",
+    within += "scala.concurrent.ExecutionContext$Implicits$"
   }
 
   executor-service-capture-on-submit {