diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/HeadLagObserver.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/HeadLagObserver.kt
index 1712585e..054c4247 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/HeadLagObserver.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/HeadLagObserver.kt
@@ -61,7 +61,6 @@ abstract class HeadLagObserver(
             .sample(throttling)
             .flatMap(this::probeFollowers)
             .map { item ->
-                log.debug("Set to ${item.t2.getId()} lag = ${item.t1}")
                 item.t2.setLag(item.t1)
             }
     }
diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/grpc/GrpcHead.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/grpc/GrpcHead.kt
index d096d9b1..7cf6e2d7 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/grpc/GrpcHead.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/grpc/GrpcHead.kt
@@ -76,7 +76,7 @@ class GrpcHead(
                     .repeat()
                     .delayElements(Duration.ofSeconds(1))
             )
-                .flatMap { it.subscribeHead(chainRef) }
+                .concatMap({ it.subscribeHead(chainRef) }, 0)
                 .doOnNext {
                     headsCounter.increment()
                 }