diff --git a/packages/protocol/contracts/L1/TaikoData.sol b/packages/protocol/contracts/L1/TaikoData.sol
index 74292083eb..d1f99416ac 100644
--- a/packages/protocol/contracts/L1/TaikoData.sol
+++ b/packages/protocol/contracts/L1/TaikoData.sol
@@ -164,6 +164,7 @@ library TaikoData {
         // this block is not verified as the last block in a batch, verifiedTransitionId
         // will remain zero.
         uint32 verifiedTransitionId;
+        uint16 minTier;
     }
 
     /// @dev Struct representing an Ethereum deposit.
diff --git a/packages/protocol/contracts/L1/libs/LibProposing.sol b/packages/protocol/contracts/L1/libs/LibProposing.sol
index 8f42af838c..54e1cfaae3 100644
--- a/packages/protocol/contracts/L1/libs/LibProposing.sol
+++ b/packages/protocol/contracts/L1/libs/LibProposing.sol
@@ -198,12 +198,18 @@ library LibProposing {
             emit CalldataTxList(meta_.id, _txList);
         }
 
+        uint16 minTier;
         {
             ITierRouter tierRouter = ITierRouter(_resolver.resolve(LibStrings.B_TIER_ROUTER, false));
             ITierProvider tierProvider = ITierProvider(tierRouter.getProvider(local.b.numBlocks));
 
-            // Use the difficulty as a random number
-            meta_.minTier = tierProvider.getMinTier(uint256(meta_.difficulty));
+            if (local.postFork) {
+                minTier =
+                    tierProvider.getMinTier(uint256(bytes32(block.prevrandao) ^ meta_.difficulty));
+            } else {
+                // Use the difficulty as a random number
+                meta_.minTier = tierProvider.getMinTier(uint256(meta_.difficulty));
+            }
         }
 
         // Create the block that will be stored onchain
@@ -217,7 +223,8 @@ library LibProposing {
             // For a new block, the next transition ID is always 1, not 0.
             nextTransitionId: 1,
             // For unverified block, its verifiedTransitionId is always 0.
-            verifiedTransitionId: 0
+            verifiedTransitionId: 0,
+            minTier: minTier
         });
 
         // Store the block in the ring buffer
diff --git a/packages/protocol/contracts/L1/libs/LibProving.sol b/packages/protocol/contracts/L1/libs/LibProving.sol
index d6b6941cef..3526b2e2cc 100644
--- a/packages/protocol/contracts/L1/libs/LibProving.sol
+++ b/packages/protocol/contracts/L1/libs/LibProving.sol
@@ -25,6 +25,7 @@ library LibProving {
         uint64 slot;
         uint64 blockId;
         uint32 tid;
+        uint16 blockMinTier;
         bool lastUnpausedAt;
         bool isTopTier;
         bool inProvingWindow;
@@ -165,6 +166,7 @@ library LibProving {
         TaikoData.Block storage blk = _state.blocks[local.slot];
 
         local.proposedAt = local.postFork ? meta.proposedAt : blk.proposedAt;
+        local.blockMinTier = meta.minTier == 0 ? blk.minTier : meta.minTier;
 
         if (LibUtils.shouldSyncStateRoot(_config.stateRootSyncInternal, local.blockId)) {
             local.stateRoot = tran.stateRoot;
@@ -197,7 +199,7 @@ library LibProving {
 
         // The new proof must meet or exceed the minimum tier required by the
         // block or the previous proof; it cannot be on a lower tier.
-        if (proof.tier == 0 || proof.tier < meta.minTier || proof.tier < ts.tier) {
+        if (proof.tier == 0 || proof.tier < local.blockMinTier || proof.tier < ts.tier) {
             revert L1_INVALID_TIER();
         }
 
@@ -208,7 +210,7 @@ library LibProving {
             ITierProvider tierProvider = ITierProvider(tierRouter.getProvider(local.blockId));
 
             local.tier = tierProvider.getTier(proof.tier);
-            local.minTier = tierProvider.getTier(meta.minTier);
+            local.minTier = tierProvider.getTier(local.blockMinTier);
         }
 
         local.inProvingWindow = !LibUtils.isPostDeadline({