diff --git a/src/miner.cpp b/src/miner.cpp
index d9b08090f2..0319388c27 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -25,6 +25,9 @@
 #include <utilmoneystr.h>
 #include <validationinterface.h>
 
+// ELEMENTS
+#include <block_proof.h> // ResetProof, ResetChallenge
+
 #include <algorithm>
 #include <queue>
 #include <utility>
@@ -96,8 +99,9 @@ void BlockAssembler::resetBlock()
     nFees = 0;
 }
 
-std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
+std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx, int min_tx_age)
 {
+    assert(min_tx_age >= 0);
     int64_t nTimeStart = GetTimeMicros();
 
     resetBlock();
@@ -142,9 +146,18 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     // transaction (which in most cases can be a no-op).
     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
 
+    if (g_signed_blocks) {
+        // Pad block weight by block proof fields (including upper-bound of signature)
+        nBlockWeight += chainparams.GetConsensus().signblockscript.size() * WITNESS_SCALE_FACTOR;
+        nBlockWeight += chainparams.GetConsensus().max_block_signature_size * WITNESS_SCALE_FACTOR;
+        // Reset block proof
+        ResetProof(*pblock);
+        ResetChallenge(*pblock, *pindexPrev, chainparams.GetConsensus());
+    }
+
     int nPackagesSelected = 0;
     int nDescendantsUpdated = 0;
-    addPackageTxs(nPackagesSelected, nDescendantsUpdated);
+    addPackageTxs(nPackagesSelected, nDescendantsUpdated, min_tx_age);
 
     int64_t nTime1 = GetTimeMicros();
 
@@ -168,10 +181,10 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     // Fill in header
     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
+    pblock->nBits          = g_signed_blocks ? 0 : GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     if (g_con_blockheightinheader) {
         pblock->block_height = nHeight;
     }
-    pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     pblock->nNonce         = 0;
     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 
@@ -306,7 +319,7 @@ void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, std::ve
 // Each time through the loop, we compare the best transaction in
 // mapModifiedTxs with the next transaction in the mempool to decide what
 // transaction package to work on next.
-void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
+void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated, int min_tx_age)
 {
     // mapModifiedTx will store sorted packages after they are modified
     // because some of their txs are already in the block
@@ -362,6 +375,12 @@ void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpda
             }
         }
 
+        // Skip transactions that are under X seconds in mempool
+        // min_tx_age value of 0 is considered "inactive", in case of mocktime
+        if (min_tx_age > 0 && iter->GetTime() > GetTime() - min_tx_age) {
+            continue;
+        }
+
         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
         // contain anything that is inBlock.
         assert(!inBlock.count(iter));
diff --git a/src/miner.h b/src/miner.h
index 8cdcf7133b..5af4c3c315 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -156,8 +156,8 @@ public:
     explicit BlockAssembler(const CChainParams& params);
     BlockAssembler(const CChainParams& params, const Options& options);
 
-    /** Construct a new block template with coinbase to scriptPubKeyIn */
-    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx=true);
+    /** Construct a new block template with coinbase to scriptPubKeyIn. min_tx_age is in seconds */
+    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx=true, int min_tx_age=0);
 
 private:
     // utility functions
@@ -170,7 +170,7 @@ private:
     /** Add transactions based on feerate including unconfirmed ancestors
       * Increments nPackagesSelected / nDescendantsUpdated with corresponding
       * statistics from the package selection (for logging statistics). */
-    void addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated) EXCLUSIVE_LOCKS_REQUIRED(mempool.cs);
+    void addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated, int required_wait=0) EXCLUSIVE_LOCKS_REQUIRED(mempool.cs);
 
     // helper functions for addPackageTxs()
     /** Remove confirmed (inBlock) entries from given set */