diff --git a/qa/rpc-tests/wallet_protectcoinbase.py b/qa/rpc-tests/wallet_protectcoinbase.py
index e05ccb529..b71a1e6f0 100755
--- a/qa/rpc-tests/wallet_protectcoinbase.py
+++ b/qa/rpc-tests/wallet_protectcoinbase.py
@@ -150,6 +150,37 @@ class WalletProtectCoinbaseTest (BitcoinTestFramework):
             errorString = e.error['message']
         assert_equal("Insufficient funds, coinbase funds can only be spent after they have been sent to a zaddr" in errorString, True)
 
+        # Verify that mempools accept tx with joinsplits which have at least the default z_sendmany fee.
+        # If this test passes, it confirms that issue #1851 has been resolved, where sending from
+        # a zaddr to 1385 taddr recipients fails because the default fee was considered too low
+        # given the tx size, resulting in mempool rejection.
+        errorString = ''
+        recipients = []
+        num_t_recipients = 2500
+        amount_per_recipient = Decimal('0.00000546') # dust threshold
+        # Note that regtest chainparams does not require standard tx, so setting the amount to be
+        # less than the dust threshold, e.g. 0.00000001 will not result in mempool rejection.
+        for i in xrange(0,num_t_recipients):
+            newtaddr = self.nodes[2].getnewaddress()
+            recipients.append({"address":newtaddr, "amount":amount_per_recipient})
+        myopid = self.nodes[0].z_sendmany(myzaddr, recipients)
+        try:
+            self.wait_and_assert_operationid_status(myopid)
+        except JSONRPCException as e:
+            print("JSONRPC error: "+e.error['message'])
+            assert(False)
+        except Exception as e:
+            print("Unexpected exception caught during testing: "+str(sys.exc_info()[0]))
+            assert(False)
+
+        self.sync_all()
+        self.nodes[1].generate(1)
+        self.sync_all()
+
+        # check balance
+        node2balance = amount_per_recipient * num_t_recipients
+        assert_equal(self.nodes[2].getbalance(), node2balance)
+
         # Send will succeed because the balance of non-coinbase utxos is 10.0
         try:
             self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 9)
@@ -161,7 +192,8 @@ class WalletProtectCoinbaseTest (BitcoinTestFramework):
         self.sync_all()
 
         # check balance
-        assert_equal(self.nodes[2].getbalance(), 9)
+        node2balance = node2balance + 9
+        assert_equal(self.nodes[2].getbalance(), node2balance)
 
         # Check that chained joinsplits in a single tx are created successfully.
         recipients = []
diff --git a/src/main.cpp b/src/main.cpp
index 612f1ed83..9c3d6e678 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -26,6 +26,7 @@
 #include "util.h"
 #include "utilmoneystr.h"
 #include "validationinterface.h"
+#include "wallet/asyncrpcoperation_sendmany.h"
 
 #include <sstream>
 
@@ -1170,12 +1171,17 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
         CTxMemPoolEntry entry(tx, nFees, GetTime(), dPriority, chainActive.Height(), mempool.HasNoInputsOf(tx));
         unsigned int nSize = entry.GetTxSize();
 
-        // Don't accept it if it can't get into a block
-        CAmount txMinFee = GetMinRelayFee(tx, nSize, true);
-        if (fLimitFree && nFees < txMinFee)
-            return state.DoS(0, error("AcceptToMemoryPool: not enough fees %s, %d < %d",
-                                      hash.ToString(), nFees, txMinFee),
-                             REJECT_INSUFFICIENTFEE, "insufficient fee");
+        // Accept a tx if it contains joinsplits and has at least the default fee specified by z_sendmany.
+        if (tx.vjoinsplit.size() > 0 && nFees >= ASYNC_RPC_OPERATION_DEFAULT_MINERS_FEE) {
+            // In future we will we have more accurate and dynamic computation of fees for tx with joinsplits.
+        } else {
+            // Don't accept it if it can't get into a block
+            CAmount txMinFee = GetMinRelayFee(tx, nSize, true);
+            if (fLimitFree && nFees < txMinFee)
+                return state.DoS(0, error("AcceptToMemoryPool: not enough fees %s, %d < %d",
+                                        hash.ToString(), nFees, txMinFee),
+                                REJECT_INSUFFICIENTFEE, "insufficient fee");
+        }
 
         // Require that free transactions have sufficient priority to be mined in the next block.
         if (GetBoolArg("-relaypriority", false) && nFees < ::minRelayTxFee.GetFee(nSize) && !AllowFree(view.GetPriority(tx, chainActive.Height() + 1))) {