diff --git a/nimbus/p2p/chain.nim b/nimbus/p2p/chain.nim
index dadc916d9..a837f1106 100644
--- a/nimbus/p2p/chain.nim
+++ b/nimbus/p2p/chain.nim
@@ -45,11 +45,13 @@ method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarr
     let vmState = newBaseVMState(head, c.db)
     let validationResult = processBlock(c.db, head, headers[i], bodies[i], vmState)
 
-    when not defined(release):
+    when not defined(release) and not defined(debugging_tool):
       if validationResult == ValidationResult.Error:
         dumpDebuggingMetaData(c.db, headers[i], bodies[i], vmState.receipts)
 
-    assert(validationResult == ValidationResult.OK)
+    if validationResult != ValidationResult.OK:
+      result = validationResult
+      return
 
     discard c.db.persistHeaderToDb(headers[i])
     if c.db.getCanonicalHead().blockHash != headers[i].blockHash:
diff --git a/premix/debug.nim b/premix/debug.nim
new file mode 100644
index 000000000..45cd16565
--- /dev/null
+++ b/premix/debug.nim
@@ -0,0 +1,46 @@
+import
+  json, os, stint, eth_trie/db, byteutils, eth_common,
+  ../nimbus/db/[db_chain], ../nimbus/p2p/chain,
+  chronicles
+
+proc prepareBlockEnv(node: JsonNode, memoryDB: TrieDatabaseRef) =
+  let state = node["state"]
+
+  for k, v in state:
+    let key = hexToSeqByte(k)
+    let value = hexToSeqByte(v.getStr())
+    memoryDB.put(key, value)
+
+proc executeBlock(memoryDB: TrieDatabaseRef, blockNumber: Uint256) =
+  let
+    chainDB = newBaseChainDB(memoryDB, false)
+    parentNumber = blockNumber - 1
+    parent = chainDB.getBlockHeader(parentNumber)
+    header = chainDB.getBlockHeader(blockNumber)
+    headerHash = header.blockHash
+    body    = chainDB.getBlockBody(headerHash)
+    chain   = newChain(chainDB)
+    headers = @[header]
+    bodies  = @[body]
+
+  chainDB.setHead(parent, true)
+  let validationResult = chain.persistBlocks(headers, bodies)
+  if validationResult != ValidationResult.OK:
+    error "block validation error", validationResult
+  else:
+    info "block validation success", validationResult, blockNumber
+
+proc main() =
+  if paramCount() == 0:
+    echo "usage: debug blockxxx.json"
+    quit(QuitFailure)
+
+  let
+    blockEnv = json.parseFile(paramStr(1))
+    memoryDB = newMemoryDB()
+    blockNumber = UInt256.fromHex(blockEnv["blockNumber"].getStr())
+
+  prepareBlockEnv(blockEnv, memoryDB)
+  executeBlock(memoryDB, blockNumber)
+
+main()
diff --git a/premix/debug.nim.cfg b/premix/debug.nim.cfg
new file mode 100644
index 000000000..a31f7504a
--- /dev/null
+++ b/premix/debug.nim.cfg
@@ -0,0 +1 @@
+-d:debugging_tool
\ No newline at end of file