diff --git a/nimbus/common/chain_config.nim b/nimbus/common/chain_config.nim
index 2d2541a74..80f69782c 100644
--- a/nimbus/common/chain_config.nim
+++ b/nimbus/common/chain_config.nim
@@ -322,7 +322,7 @@ proc chainConfigForNetwork*(id: NetworkId): ChainConfig =
 
   result = case id
   of MainNet:
-    const mainNetTTD = UInt256.fromHex("58750000000000000000000")
+    const mainNetTTD = parse("58750000000000000000000",UInt256)
     ChainConfig(
       consensusType:       ConsensusType.POW,
       chainId:             MainNet.ChainId,