diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1904,14 +1904,6 @@
              MILLI * (nTime6 - nTime5), nTimeCallbacks * MICRO,
              nTimeCallbacks * MILLI / nBlocksTotal);
 
-    // If we just activated the replay protection with that block, it means
-    // transaction in the mempool are now invalid. As a result, we need to clear
-    // the mempool.
-    if (IsReplayProtectionEnabled(config, pindex) &&
-        !IsReplayProtectionEnabled(config, pindex->pprev)) {
-        g_mempool.clear();
-    }
-
     return true;
 }
 
@@ -2404,6 +2396,8 @@
                        const std::shared_ptr<const CBlock> &pblock,
                        ConnectTrace &connectTrace,
                        DisconnectedBlockTransactions &disconnectpool) {
+    AssertLockHeld(cs_main);
+
     assert(pindexNew->pprev == chainActive.Tip());
     // Read block from disk.
     int64_t nTime1 = GetTimeMicros();
@@ -2480,6 +2474,14 @@
              (nTime5 - nTime4) * MILLI, nTimeChainState * MICRO,
              nTimeChainState * MILLI / nBlocksTotal);
 
+    // If we just activated the replay protection with that block, it means
+    // transaction in the mempool are now invalid. As a result, we need to clear
+    // the mempool.
+    if (IsReplayProtectionEnabled(config, pindexNew) &&
+        !IsReplayProtectionEnabled(config, pindexNew->pprev)) {
+        g_mempool.clear();
+    }
+
     // Remove conflicting transactions from the mempool.;
     g_mempool.removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
     disconnectpool.removeForBlock(blockConnecting.vtx);
diff --git a/test/functional/abc-replay-protection.py b/test/functional/abc-replay-protection.py
--- a/test/functional/abc-replay-protection.py
+++ b/test/functional/abc-replay-protection.py
@@ -234,6 +234,10 @@
         block(5556)
         yield accepted()
 
+        # Check we just activated the replay protection
+        assert_equal(node.getblockheader(node.getbestblockhash())['mediantime'],
+                     REPLAY_PROTECTION_START_TIME)
+
         # Non replay protected transactions are not valid anymore,
         # so they should be removed from the mempool.
         assert(tx_id not in set(node.getrawmempool()))
@@ -252,8 +256,27 @@
         tip(5556)
 
         # The replay protected transaction is now valid
-        send_transaction_to_mempool(replay_txns[0])
-        replay_tx_id = send_transaction_to_mempool(replay_txns[1])
+        replay_tx0_id = send_transaction_to_mempool(replay_txns[0])
+        replay_tx1_id = send_transaction_to_mempool(replay_txns[1])
+
+        # Make sure the transaction are ready to be mined.
+        tmpl = node.getblocktemplate()
+
+        found_id0 = False
+        found_id1 = False
+
+        for txn in tmpl['transactions']:
+            txid = txn['txid']
+            if txid == replay_tx0_id:
+                found_id0 = True
+            elif txid == replay_tx1_id:
+                found_id1 = True
+
+        assert(found_id0 and found_id1)
+
+        # And the mempool is still in good shape.
+        assert(replay_tx0_id in set(node.getrawmempool()))
+        assert(replay_tx1_id in set(node.getrawmempool()))
 
         # They also can also be mined
         b5 = block(5)
@@ -263,18 +286,21 @@
         # Ok, now we check if a reorg work properly accross the activation.
         postforkblockid = node.getbestblockhash()
         node.invalidateblock(postforkblockid)
-        assert(replay_tx_id in set(node.getrawmempool()))
+        assert(replay_tx0_id in set(node.getrawmempool()))
+        assert(replay_tx1_id in set(node.getrawmempool()))
 
         # Deactivating replay protection.
         forkblockid = node.getbestblockhash()
         node.invalidateblock(forkblockid)
-        assert(replay_tx_id not in set(node.getrawmempool()))
+        assert(replay_tx0_id not in set(node.getrawmempool()))
+        assert(replay_tx1_id not in set(node.getrawmempool()))
 
         # Check that we also do it properly on deeper reorg.
         node.reconsiderblock(forkblockid)
         node.reconsiderblock(postforkblockid)
         node.invalidateblock(forkblockid)
-        assert(replay_tx_id not in set(node.getrawmempool()))
+        assert(replay_tx0_id not in set(node.getrawmempool()))
+        assert(replay_tx1_id not in set(node.getrawmempool()))
 
 
 if __name__ == '__main__':