diff --git a/Libplanet/HashDigest.cs b/Libplanet/HashDigest.cs
index 08f9b09c8f..889ef33cd1 100644
--- a/Libplanet/HashDigest.cs
+++ b/Libplanet/HashDigest.cs
@@ -163,8 +163,8 @@ public bool LessThanTarget(long difficulty)
                 return true;
             }
 
-            var target = new BigInteger(
-                Math.Pow(2, 256) / difficulty);
+            double maxTarget = Math.Pow(2, 256);
+            var target = new BigInteger(maxTarget / difficulty);
 
             // Add zero to convert unsigned BigInteger
             var result = new BigInteger(ByteArray.Add(0).ToArray());