diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index 8956ea1b..8a3f6cb4 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -968,7 +968,7 @@ Chain.prototype.setBestChain = async function setBestChain(entry, block, prev, f
   // Warn of unknown versionbits.
   if (entry.hasUnknown()) {
     this.logger.warning(
-      'Unknown version bits in block %d: %d.',
+      'Unknown version bits in block %d: %s.',
       entry.height, util.hex32(entry.version));
   }
 
@@ -1033,8 +1033,8 @@ Chain.prototype.saveAlternate = async function saveAlternate(entry, block, prev,
   // Warn of unknown versionbits.
   if (entry.hasUnknown()) {
     this.logger.warning(
-      'Unknown version bits in block %d: %d.',
-      entry.height, entry.version);
+      'Unknown version bits in block %d: %s.',
+      entry.height, util.hex32(entry.version));
   }
 
   await this.db.save(entry, block);