diff --git a/contracts/standard/rng/BeaconRNG.sol b/contracts/standard/rng/BeaconRNG.sol
index 071c7245..24617773 100644
--- a/contracts/standard/rng/BeaconRNG.sol
+++ b/contracts/standard/rng/BeaconRNG.sol
@@ -39,7 +39,7 @@ contract BeaconRNG {
      */
     function getUncorrelatedRN(uint _block) public returns (uint) {
         // Pre-Merge.
-        if (block.difficulty <= 2**64) {
+        if (block.difficulty < 18_446_744_073_709_551_617) { // block.difficulty <= 2**64
             uint baseRN = blockhashRNGFallback.getRN(_block);
             if (baseRN == 0) {
                 return 0;