diff --git a/src/validation.cpp b/src/validation.cpp
index b8fcc68d21..170e0b36e1 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -709,6 +709,8 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         std::string errString;
         if (!pool.CalculateMemPoolAncestors(entry, setAncestors, nLimitAncestors, nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, errString)) {
             setAncestors.clear();
+            // If CalculateMemPoolAncestors fails second time, we want the original error string.
+            std::string dummy_err_string;
             // If the new transaction is relatively small (up to 40k weight)
             // and has at most one ancestor (ie ancestor limit of 2, including
             // the new transaction), allow it if its parent has exactly the
@@ -720,7 +722,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
             // outputs - one for each counterparty. For more info on the uses for
             // this, see https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-November/016518.html
             if (nSize >  EXTRA_DESCENDANT_TX_SIZE_LIMIT ||
-                    !pool.CalculateMemPoolAncestors(entry, setAncestors, 2, nLimitAncestorSize, nLimitDescendants + 1, nLimitDescendantSize + EXTRA_DESCENDANT_TX_SIZE_LIMIT, errString)) {
+                    !pool.CalculateMemPoolAncestors(entry, setAncestors, 2, nLimitAncestorSize, nLimitDescendants + 1, nLimitDescendantSize + EXTRA_DESCENDANT_TX_SIZE_LIMIT, dummy_err_string)) {
                 return state.DoS(0, false, REJECT_NONSTANDARD, "too-long-mempool-chain", false, errString);
             }
         }
diff --git a/test/functional/mempool_package_onemore.py b/test/functional/mempool_package_onemore.py
index 962f902047..464e163596 100755
--- a/test/functional/mempool_package_onemore.py
+++ b/test/functional/mempool_package_onemore.py
@@ -66,14 +66,14 @@ class MempoolPackagesTest(BitcoinTestFramework):
         assert_equal(len(self.nodes[0].getrawmempool(True)), MAX_ANCESTORS + 1)
 
         # Adding one more transaction on to the chain should fail.
-        assert_raises_rpc_error(-26, "too-long-mempool-chain", self.chain_transaction, self.nodes[0], [txid], [0], value, fee, 1)
+        assert_raises_rpc_error(-26, "too-long-mempool-chain, too many unconfirmed ancestors [limit: 25]", self.chain_transaction, self.nodes[0], [txid], [0], value, fee, 1)
         # ...even if it chains on from some point in the middle of the chain.
-        assert_raises_rpc_error(-26, "too-long-mempool-chain", self.chain_transaction, self.nodes[0], [chain[2][0]], [1], chain[2][1], fee, 1)
-        assert_raises_rpc_error(-26, "too-long-mempool-chain", self.chain_transaction, self.nodes[0], [chain[1][0]], [1], chain[1][1], fee, 1)
+        assert_raises_rpc_error(-26, "too-long-mempool-chain, too many descendants", self.chain_transaction, self.nodes[0], [chain[2][0]], [1], chain[2][1], fee, 1)
+        assert_raises_rpc_error(-26, "too-long-mempool-chain, too many descendants", self.chain_transaction, self.nodes[0], [chain[1][0]], [1], chain[1][1], fee, 1)
         # ...even if it chains on to two parent transactions with one in the chain.
-        assert_raises_rpc_error(-26, "too-long-mempool-chain", self.chain_transaction, self.nodes[0], [chain[0][0], second_chain], [1, 0], chain[0][1] + second_chain_value, fee, 1)
+        assert_raises_rpc_error(-26, "too-long-mempool-chain, too many descendants", self.chain_transaction, self.nodes[0], [chain[0][0], second_chain], [1, 0], chain[0][1] + second_chain_value, fee, 1)
         # ...especially if its > 40k weight
-        assert_raises_rpc_error(-26, "too-long-mempool-chain", self.chain_transaction, self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 350)
+        assert_raises_rpc_error(-26, "too-long-mempool-chain, too many descendants", self.chain_transaction, self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 350)
         # But not if it chains directly off the first transaction
         self.chain_transaction(self.nodes[0], [chain[0][0]], [1], chain[0][1], fee, 1)
         # and the second chain should work just fine