diff --git a/qa/rpc-tests/autoix-mempool.py b/qa/rpc-tests/autoix-mempool.py
index fdd3a57f3..f79fe772a 100755
--- a/qa/rpc-tests/autoix-mempool.py
+++ b/qa/rpc-tests/autoix-mempool.py
@@ -122,6 +122,21 @@ class AutoIXMempoolTest(DashTestFramework):
     def run_test(self):
         # make sure masternodes are synced
         sync_masternodes(self.nodes)
+
+        self.nodes[0].spork("SPORK_17_QUORUM_DKG_ENABLED", 0)
+        self.wait_for_sporks_same()
+        self.mine_quorum()
+
+        print("Test old InstantSend")
+        self.test_auto();
+
+        self.nodes[0].spork("SPORK_2_INSTANTSEND_ENABLED", 1)
+        self.wait_for_sporks_same()
+
+        print("Test new InstantSend")
+        self.test_auto(True);
+
+    def test_auto(self, new_is = False):
         self.activate_autoix_bip9()
         self.set_autoix_spork_state(True)
 
@@ -151,8 +166,8 @@ class AutoIXMempoolTest(DashTestFramework):
 
         # autoIX is not working now
         assert(not self.send_simple_tx(sender, receiver))
-        # regular IX is still working
-        assert(self.send_regular_IX(sender, receiver))
+        # regular IX is still working for old IS but not for new one
+        assert(not self.send_regular_IX(sender, receiver) if new_is else self.send_regular_IX(sender, receiver))
 
         # generate one block to clean up mempool and retry auto and regular IX
         # generate 2 more blocks to have enough confirmations for IX
diff --git a/src/instantx.h b/src/instantx.h
index c8c0aa585..aac54e2d1 100644
--- a/src/instantx.h
+++ b/src/instantx.h
@@ -45,11 +45,12 @@ extern int nCompleteTXLocks;
  */
 class CInstantSend
 {
-private:
-    static const std::string SERIALIZATION_VERSION_STRING;
+public:
     /// Automatic locks of "simple" transactions are only allowed
     /// when mempool usage is lower than this threshold
     static const double AUTO_IX_MEMPOOL_THRESHOLD;
+private:
+    static const std::string SERIALIZATION_VERSION_STRING;
 
     // Keep track of current block height
     int nCachedBlockHeight;
diff --git a/src/llmq/quorums_instantsend.cpp b/src/llmq/quorums_instantsend.cpp
index 6104f5b32..7f0a322ac 100644
--- a/src/llmq/quorums_instantsend.cpp
+++ b/src/llmq/quorums_instantsend.cpp
@@ -137,6 +137,10 @@ bool CInstantSendManager::ProcessTx(CNode* pfrom, const CTransaction& tx, CConnm
 
 bool CInstantSendManager::CheckCanLock(const CTransaction& tx, bool printDebug, const Consensus::Params& params)
 {
+    if (sporkManager.IsSporkActive(SPORK_16_INSTANTSEND_AUTOLOCKS) && (mempool.UsedMemoryShare() > CInstantSend::AUTO_IX_MEMPOOL_THRESHOLD)) {
+        return false;
+    }
+
     int nInstantSendConfirmationsRequired = params.nInstantSendConfirmationsRequired;
 
     uint256 txHash = tx.GetHash();