diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetector.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetector.kt
index f923c4bf5..afffb61d1 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetector.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetector.kt
@@ -1,14 +1,12 @@
 package io.emeraldpay.dshackle.upstream.ethereum
 
+import com.fasterxml.jackson.module.kotlin.readValue
 import io.emeraldpay.dshackle.Chain
 import io.emeraldpay.dshackle.Global
 import io.emeraldpay.dshackle.upstream.ChainRequest
-import io.emeraldpay.dshackle.upstream.ChainResponse
 import io.emeraldpay.dshackle.upstream.Upstream
 import io.emeraldpay.dshackle.upstream.ethereum.json.BlockJson
 import io.emeraldpay.dshackle.upstream.ethereum.json.TransactionRefJson
-import io.emeraldpay.dshackle.upstream.ethereum.rpc.RpcException
-import io.emeraldpay.dshackle.upstream.ethereum.rpc.RpcResponseError
 import io.emeraldpay.dshackle.upstream.finalization.FinalizationData
 import io.emeraldpay.dshackle.upstream.finalization.FinalizationDetector
 import io.emeraldpay.dshackle.upstream.finalization.FinalizationType
@@ -74,35 +72,28 @@ class EthereumFinalizationDetector : FinalizationDetector {
                         upstream
                             .getIngressReader()
                             .read(req)
-                            .onErrorResume {
-                                if (it.message != null && it.message!!.matches(Regex(errorRegex))) {
-                                    log.warn("Can't retrieve tagged block, finalization detector for upstream ${upstream.getId()} $chain tag $type disabled")
-                                    disableDetector[type] = true
-                                } else {
-                                    throw it
-                                }
-                                Mono.empty<ChainResponse>()
-                            }
                             .flatMap {
-                                it.requireResult().map { result ->
-                                    val block = Global.objectMapper
-                                        .readValue(
-                                            result,
-                                            BlockJson::class.java,
-                                        ) as BlockJson<TransactionRefJson>?
+                                it.requireResult().flatMap { result ->
+                                    val block = Global.objectMapper.readValue<BlockJson<TransactionRefJson>>(result)
                                     if (block != null) {
-                                        FinalizationData(block.number, type)
+                                        Mono.just(FinalizationData(block.number, type))
                                     } else {
-                                        throw RpcException(RpcResponseError.CODE_INVALID_JSON, "can't parse block data")
+                                        Mono.empty()
                                     }
                                 }
                             }
+                            .onErrorResume {
+                                if (it.message != null && it.message!!.matches(Regex(errorRegex))) {
+                                    log.warn("Can't retrieve tagged block, finalization detector of upstream {} tag {} is disabled", upstream.getId(), type)
+                                    disableDetector[type] = true
+                                } else {
+                                    log.error("Error in FinalizationDetector of upstream {}, reason - {}", upstream.getId(), it.message)
+                                }
+                                Mono.empty()
+                            }
                     } else {
                         Flux.empty()
                     }
-                }.onErrorResume {
-                    log.error("Error in FinalizationDetector for upstream ${upstream.getId()} $chain — $it")
-                    Flux.empty()
                 }
             }.filter {
                 it.height > (data[it.type]?.height ?: 0)
diff --git a/src/test/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetectorTest.kt b/src/test/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetectorTest.kt
index f109645a5..c18284f2f 100644
--- a/src/test/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetectorTest.kt
+++ b/src/test/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFinalizationDetectorTest.kt
@@ -3,6 +3,7 @@ package io.emeraldpay.dshackle.upstream.ethereum
 import io.emeraldpay.dshackle.Chain
 import io.emeraldpay.dshackle.Global
 import io.emeraldpay.dshackle.reader.ChainReader
+import io.emeraldpay.dshackle.upstream.ChainCallError
 import io.emeraldpay.dshackle.upstream.ChainRequest
 import io.emeraldpay.dshackle.upstream.ChainResponse
 import io.emeraldpay.dshackle.upstream.Upstream
@@ -14,6 +15,8 @@ import io.emeraldpay.dshackle.upstream.rpcclient.ListParams
 import org.junit.jupiter.api.Test
 import org.mockito.kotlin.doReturn
 import org.mockito.kotlin.mock
+import org.mockito.kotlin.times
+import org.mockito.kotlin.verify
 import reactor.core.publisher.Mono
 import reactor.test.StepVerifier
 import java.time.Duration
@@ -54,6 +57,94 @@ class EthereumFinalizationDetectorTest {
             .verify(Duration.ofSeconds(1))
     }
 
+    @Test
+    fun `safe and finalized blocks returns null`() {
+        val reader = mock<ChainReader> {
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+            } doReturn Mono.just(ChainResponse(Global.nullValue, null)) doReturn Mono.just(ChainResponse(Global.nullValue, null))
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+            } doReturn Mono.just(ChainResponse(Global.nullValue, null)) doReturn Mono.just(ChainResponse(Global.nullValue, null))
+        }
+        val upstream = mock<Upstream> {
+            on { getIngressReader() } doReturn reader
+        }
+
+        val detector = EthereumFinalizationDetector()
+
+        StepVerifier.withVirtualTime { detector.detectFinalization(upstream, Duration.ofSeconds(10), Chain.ZKSYNC__MAINNET) }
+            .expectSubscription()
+            .thenAwait(Duration.ofSeconds(0))
+            .expectNoEvent(Duration.ofMillis(50))
+            .thenAwait(Duration.ofSeconds(15))
+            .expectNoEvent(Duration.ofMillis(50))
+            .thenCancel()
+            .verify(Duration.ofSeconds(1))
+
+        verify(reader, times(2)).read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+        verify(reader, times(2)).read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+    }
+
+    @Test
+    fun `disable detector if receive specific errors`() {
+        val reader = mock<ChainReader> {
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+            } doReturn Mono.just(ChainResponse(null, ChainCallError(1, "Got an invalid block number, check it")))
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+            } doReturn response(2) doReturn response(10)
+        }
+
+        val upstream = mock<Upstream> {
+            on { getIngressReader() } doReturn reader
+        }
+
+        val detector = EthereumFinalizationDetector()
+
+        StepVerifier.withVirtualTime { detector.detectFinalization(upstream, Duration.ofSeconds(10), Chain.ZKSYNC__MAINNET) }
+            .expectSubscription()
+            .thenAwait(Duration.ofSeconds(0))
+            .expectNext(FinalizationData(2L, FinalizationType.FINALIZED_BLOCK))
+            .thenAwait(Duration.ofSeconds(15))
+            .expectNext(FinalizationData(10L, FinalizationType.FINALIZED_BLOCK))
+            .thenCancel()
+            .verify(Duration.ofSeconds(1))
+
+        verify(reader).read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+        verify(reader, times(2)).read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+    }
+
+    @Test
+    fun `ignore response if it cannot be parsed`() {
+        val reader = mock<ChainReader> {
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+            } doReturn Mono.just(ChainResponse("""{"name": "value"}""".toByteArray(), null)) doReturn Mono.just(ChainResponse("""{"name": "value"}""".toByteArray(), null))
+            on {
+                read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+            } doReturn response(2) doReturn response(10)
+        }
+        val upstream = mock<Upstream> {
+            on { getIngressReader() } doReturn reader
+        }
+
+        val detector = EthereumFinalizationDetector()
+
+        StepVerifier.withVirtualTime { detector.detectFinalization(upstream, Duration.ofSeconds(10), Chain.ZKSYNC__MAINNET) }
+            .expectSubscription()
+            .thenAwait(Duration.ofSeconds(0))
+            .expectNext(FinalizationData(2L, FinalizationType.FINALIZED_BLOCK))
+            .thenAwait(Duration.ofSeconds(15))
+            .expectNext(FinalizationData(10L, FinalizationType.FINALIZED_BLOCK))
+            .thenCancel()
+            .verify(Duration.ofSeconds(1))
+
+        verify(reader, times(2)).read(ChainRequest("eth_getBlockByNumber", ListParams("safe", false), 1))
+        verify(reader, times(2)).read(ChainRequest("eth_getBlockByNumber", ListParams("finalized", false), 2))
+    }
+
     private fun response(blockNumber: Long) =
         Mono.just(
             ChainResponse(