diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/MergedHead.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/MergedHead.kt
index 0c87de88..1518f579 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/MergedHead.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/MergedHead.kt
@@ -16,6 +16,7 @@
  */
 package io.emeraldpay.dshackle.upstream
 
+import com.google.common.annotations.VisibleForTesting
 import io.emeraldpay.dshackle.cache.Caches
 import io.emeraldpay.dshackle.cache.CachesEnabled
 import io.emeraldpay.dshackle.upstream.forkchoice.ForkChoice
@@ -61,4 +62,8 @@ class MergedHead(
             }
         }
     }
+
+    @VisibleForTesting
+    private fun getSources() =
+        sources
 }
diff --git a/src/test/groovy/io/emeraldpay/dshackle/upstream/MultistreamSpec.groovy b/src/test/groovy/io/emeraldpay/dshackle/upstream/MultistreamSpec.groovy
index ee9790e9..8a28f4b3 100644
--- a/src/test/groovy/io/emeraldpay/dshackle/upstream/MultistreamSpec.groovy
+++ b/src/test/groovy/io/emeraldpay/dshackle/upstream/MultistreamSpec.groovy
@@ -203,34 +203,19 @@ class MultistreamSpec extends Specification {
 
     def "Filter upstream matching selector single"() {
         setup:
-
-        def block1 = createBlock(111111)
-        def block2 = createBlock(222222)
-        def block3 = createBlock(222222)
-
-        def up1 = TestingCommons.upstream("test-1", "internal").tap {
-            it.ethereumHeadMock.predefined = Flux.just(block1)
-        }
-        def up2 = TestingCommons.upstream("test-2", "external").tap {
-            it.ethereumHeadMock.predefined = Flux.just(block2)
-        }
-        def up3 = TestingCommons.upstream("test-3", "external").tap {
-            it.ethereumHeadMock.predefined = Flux.just(block3)
-        }
+        def up1 = TestingCommons.upstream("test-1", "internal")
+        def up2 = TestingCommons.upstream("test-2", "external")
+        def up3 = TestingCommons.upstream("test-3", "external")
         def multistream = new EthereumPosMultiStream(Chain.ETHEREUM, [up1, up2, up3], Caches.default())
 
+        expect:
+        multistream.getHead(new Selector.LabelMatcher("provider", ["internal"])).is(up1.ethereumHeadMock)
+        multistream.getHead(new Selector.LabelMatcher("provider", ["unknown"])) in EmptyHead
 
-        up1.ethereumHeadMock.toString()
-
-        when:
-        def head = multistream.getHead(new Selector.LabelMatcher("provider", ["internal"])).flux
-
-        then:
-        StepVerifier.create(head)
-                .expectNext(block1)
-                .expectNext(block1)
-                .expectComplete()
-                .verify(Duration.ofSeconds(1))
+        def head = multistream.getHead(new Selector.LabelMatcher("provider", ["external"]))
+        head in MergedHead
+        (head as MergedHead).isRunning()
+        (head as MergedHead).getSources().sort() == [up2.ethereumHeadMock, up3.ethereumHeadMock].sort()
 
     }