diff --git a/src/wallet/gtest/test_wallet.cpp b/src/wallet/gtest/test_wallet.cpp
index 8db093e7..56ec6337 100644
--- a/src/wallet/gtest/test_wallet.cpp
+++ b/src/wallet/gtest/test_wallet.cpp
@@ -3,6 +3,7 @@
 
 #include "base58.h"
 #include "chainparams.h"
+#include "main.h"
 #include "random.h"
 #include "wallet/wallet.h"
 #include "zcash/JoinSplit.hpp"
@@ -78,6 +79,55 @@ libzcash::Note GetNote(const libzcash::SpendingKey& sk,
     return note_pt.note(sk.address());
 }
 
+CWalletTx GetValidSpend(const libzcash::SpendingKey& sk,
+                        const libzcash::Note& note, CAmount value) {
+    CMutableTransaction mtx;
+    mtx.vout.resize(2);
+    mtx.vout[0].nValue = value;
+    mtx.vout[1].nValue = 0;
+
+    // Generate an ephemeral keypair.
+    uint256 joinSplitPubKey;
+    unsigned char joinSplitPrivKey[crypto_sign_SECRETKEYBYTES];
+    crypto_sign_keypair(joinSplitPubKey.begin(), joinSplitPrivKey);
+    mtx.joinSplitPubKey = joinSplitPubKey;
+
+    // Fake tree for the unused witness
+    ZCIncrementalMerkleTree tree;
+
+    boost::array<libzcash::JSInput, 2> inputs = {
+        libzcash::JSInput(tree.witness(), note, sk),
+        libzcash::JSInput() // dummy input
+    };
+
+    boost::array<libzcash::JSOutput, 2> outputs = {
+        libzcash::JSOutput(), // dummy output
+        libzcash::JSOutput() // dummy output
+    };
+
+    boost::array<libzcash::Note, 2> output_notes;
+
+    // Prepare JoinSplits
+    uint256 rt;
+    JSDescription jsdesc {*params, mtx.joinSplitPubKey, rt,
+                          inputs, outputs, 0, value, false};
+    mtx.vjoinsplit.push_back(jsdesc);
+
+    // Empty output script.
+    CScript scriptCode;
+    CTransaction signTx(mtx);
+    uint256 dataToBeSigned = SignatureHash(scriptCode, signTx, NOT_AN_INPUT, SIGHASH_ALL);
+
+    // Add the signature
+    assert(crypto_sign_detached(&mtx.joinSplitSig[0], NULL,
+                         dataToBeSigned.begin(), 32,
+                         joinSplitPrivKey
+                        ) == 0);
+    CTransaction tx {mtx};
+    CWalletTx wtx {NULL, tx};
+    return wtx;
+}
+
 TEST(wallet_tests, set_note_addrs_in_cwallettx) {
     auto sk = libzcash::SpendingKey::random();
     auto wtx = GetValidReceive(sk, 10, true);
@@ -125,3 +175,74 @@ TEST(wallet_tests, find_note_in_tx) {
     EXPECT_EQ(1, noteMap.count(jsoutpt));
     EXPECT_EQ(nd, noteMap[jsoutpt]);
 }
+
+TEST(wallet_tests, get_conflicted_notes) {
+    CWallet wallet;
+
+    auto sk = libzcash::SpendingKey::random();
+    wallet.AddSpendingKey(sk);
+
+    auto wtx = GetValidReceive(sk, 10, true);
+    auto note = GetNote(sk, wtx, 0, 1);
+    auto nullifier = note.nullifier(sk);
+
+    auto wtx2 = GetValidSpend(sk, note, 5);
+    auto wtx3 = GetValidSpend(sk, note, 10);
+    auto hash2 = wtx2.GetTxid();
+    auto hash3 = wtx3.GetTxid();
+
+    // No conflicts for no spends
+    EXPECT_EQ(0, wallet.GetConflicts(hash2).size());
+    wallet.AddToWallet(wtx, true, NULL);
+    EXPECT_EQ(0, wallet.GetConflicts(hash2).size());
+
+    // No conflicts for one spend
+    wallet.AddToWallet(wtx2, true, NULL);
+    EXPECT_EQ(0, wallet.GetConflicts(hash2).size());
+
+    // Conflicts for two spends
+    wallet.AddToWallet(wtx3, true, NULL);
+    auto c3 = wallet.GetConflicts(hash2);
+    EXPECT_EQ(2, c3.size());
+    EXPECT_EQ(std::set<uint256>({hash2, hash3}), c3);
+}
+
+TEST(wallet_tests, nullifier_is_spent) {
+    CWallet wallet;
+
+    auto sk = libzcash::SpendingKey::random();
+    wallet.AddSpendingKey(sk);
+
+    auto wtx = GetValidReceive(sk, 10, true);
+    auto note = GetNote(sk, wtx, 0, 1);
+    auto nullifier = note.nullifier(sk);
+
+    EXPECT_FALSE(wallet.IsSpent(nullifier));
+
+    wallet.AddToWallet(wtx, true, NULL);
+    EXPECT_FALSE(wallet.IsSpent(nullifier));
+
+    auto wtx2 = GetValidSpend(sk, note, 5);
+    wallet.AddToWallet(wtx2, true, NULL);
+    EXPECT_FALSE(wallet.IsSpent(nullifier));
+
+    // Fake-mine the transaction
+    EXPECT_EQ(-1, chainActive.Height());
+    CBlock block;
+    block.vtx.push_back(wtx2);
+    block.hashMerkleRoot = block.BuildMerkleTree();
+    auto blockHash = block.GetHash();
+    CBlockIndex fakeIndex {block};
+    mapBlockIndex.insert(std::make_pair(blockHash, &fakeIndex));
+    chainActive.SetTip(&fakeIndex);
+    EXPECT_TRUE(chainActive.Contains(&fakeIndex));
+    EXPECT_EQ(0, chainActive.Height());
+
+    wtx2.SetMerkleBranch(block);
+    wallet.AddToWallet(wtx2, true, NULL);
+    EXPECT_TRUE(wallet.IsSpent(nullifier));
+
+    // Tear down
+    chainActive.SetTip(NULL);
+    mapBlockIndex.erase(blockHash);
+}
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 0d287dac..7da567ee 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -401,6 +401,20 @@ set<uint256> CWallet::GetConflicts(const uint256& txid) const
         for (TxSpends::const_iterator it = range.first; it != range.second; ++it)
             result.insert(it->second);
     }
+
+    std::pair<TxNullifiers::const_iterator, TxNullifiers::const_iterator> range_n;
+
+    for (const JSDescription& jsdesc : wtx.vjoinsplit) {
+        for (const uint256& nullifier : jsdesc.nullifiers) {
+            if (mapTxNullifiers.count(nullifier) <= 1) {
+                continue;  // No conflict if zero or one spends
+            }
+            range_n = mapTxNullifiers.equal_range(nullifier);
+            for (TxNullifiers::const_iterator it = range_n.first; it != range_n.second; ++it) {
+                result.insert(it->second);
+            }
+        }
+    }
     return result;
 }
 
@@ -456,7 +470,8 @@ bool CWallet::Verify(const string& walletFile, string& warningString, string& er
     return true;
 }
 
-void CWallet::SyncMetaData(pair<TxSpends::iterator, TxSpends::iterator> range)
+template <class T>
+void CWallet::SyncMetaData(pair<typename TxSpendMap<T>::iterator, typename TxSpendMap<T>::iterator> range)
 {
     // We want all the wallet transactions in range to have the same metadata as
     // the oldest (smallest nOrderPos).
@@ -464,7 +479,7 @@ void CWallet::SyncMetaData(pair<TxSpends::iterator, TxSpends::iterator> range)
 
     int nMinOrderPos = std::numeric_limits<int>::max();
     const CWalletTx* copyFrom = NULL;
-    for (TxSpends::iterator it = range.first; it != range.second; ++it)
+    for (typename TxSpendMap<T>::iterator it = range.first; it != range.second; ++it)
     {
         const uint256& hash = it->second;
         int n = mapWallet[hash].nOrderPos;
@@ -475,7 +490,7 @@ void CWallet::SyncMetaData(pair<TxSpends::iterator, TxSpends::iterator> range)
         }
     }
     // Now copy data from copyFrom to rest:
-    for (TxSpends::iterator it = range.first; it != range.second; ++it)
+    for (typename TxSpendMap<T>::iterator it = range.first; it != range.second; ++it)
     {
         const uint256& hash = it->second;
         CWalletTx* copyTo = &mapWallet[hash];
@@ -514,15 +529,42 @@ bool CWallet::IsSpent(const uint256& hash, unsigned int n) const
     return false;
 }
 
+/**
+ * Note is spent if any non-conflicted transaction
+ * spends it:
+ */
+bool CWallet::IsSpent(const uint256& nullifier) const
+{
+    pair<TxNullifiers::const_iterator, TxNullifiers::const_iterator> range;
+    range = mapTxNullifiers.equal_range(nullifier);
+
+    for (TxNullifiers::const_iterator it = range.first; it != range.second; ++it) {
+        const uint256& wtxid = it->second;
+        std::map<uint256, CWalletTx>::const_iterator mit = mapWallet.find(wtxid);
+        if (mit != mapWallet.end() && mit->second.GetDepthInMainChain() >= 0) {
+            return true; // Spent
+        }
+    }
+    return false;
+}
+
 void CWallet::AddToSpends(const COutPoint& outpoint, const uint256& wtxid)
 {
     mapTxSpends.insert(make_pair(outpoint, wtxid));
 
     pair<TxSpends::iterator, TxSpends::iterator> range;
     range = mapTxSpends.equal_range(outpoint);
-    SyncMetaData(range);
+    SyncMetaData<COutPoint>(range);
 }
 
+void CWallet::AddToSpends(const uint256& nullifier, const uint256& wtxid)
+{
+    mapTxNullifiers.insert(make_pair(nullifier, wtxid));
+
+    pair<TxNullifiers::iterator, TxNullifiers::iterator> range;
+    range = mapTxNullifiers.equal_range(nullifier);
+    SyncMetaData<uint256>(range);
+}
 
 void CWallet::AddToSpends(const uint256& wtxid)
 {
@@ -531,8 +573,14 @@ void CWallet::AddToSpends(const uint256& wtxid)
     if (thisTx.IsCoinBase()) // Coinbases don't spend anything!
         return;
 
-    BOOST_FOREACH(const CTxIn& txin, thisTx.vin)
+    for (const CTxIn& txin : thisTx.vin) {
         AddToSpends(txin.prevout, wtxid);
+    }
+    for (const JSDescription& jsdesc : thisTx.vjoinsplit) {
+        for (const uint256& nullifier : jsdesc.nullifiers) {
+            AddToSpends(nullifier, wtxid);
+        }
+    }
 }
 
 bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 6b118b9c..5c94655e 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -548,17 +548,28 @@ private:
     int64_t nLastResend;
     bool fBroadcastTransactions;
 
+    template <class T>
+    using TxSpendMap = std::multimap<T, uint256>;
     /**
      * Used to keep track of spent outpoints, and
      * detect and report conflicts (double-spends or
      * mutated transactions where the mutant gets mined).
      */
-    typedef std::multimap<COutPoint, uint256> TxSpends;
+    typedef TxSpendMap<COutPoint> TxSpends;
     TxSpends mapTxSpends;
+    /**
+     * Used to keep track of spent Notes, and
+     * detect and report conflicts (double-spends).
+     */
+    typedef TxSpendMap<uint256> TxNullifiers;
+    TxNullifiers mapTxNullifiers;
+
     void AddToSpends(const COutPoint& outpoint, const uint256& wtxid);
+    void AddToSpends(const uint256& nullifier, const uint256& wtxid);
     void AddToSpends(const uint256& wtxid);
 
-    void SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator>);
+    template <class T>
+    void SyncMetaData(std::pair<typename TxSpendMap<T>::iterator, typename TxSpendMap<T>::iterator>);
 
 public:
     /*
@@ -636,6 +647,7 @@ public:
     bool SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int nConfTheirs, std::vector<COutput> vCoins, std::set<std::pair<const CWalletTx*,unsigned int> >& setCoinsRet, CAmount& nValueRet) const;
 
     bool IsSpent(const uint256& hash, unsigned int n) const;
+    bool IsSpent(const uint256& nullifier) const;
 
     bool IsLockedCoin(uint256 hash, unsigned int n) const;
     void LockCoin(COutPoint& output);