diff --git a/src/rpc/index_util.cpp b/src/rpc/index_util.cpp
index 65ddf3e49b..4b8bf64a61 100644
--- a/src/rpc/index_util.cpp
+++ b/src/rpc/index_util.cpp
@@ -33,7 +33,7 @@ bool GetAddressUnspentIndex(uint160 addressHash, AddressType type,
     return true;
 }
 
-bool GetSpentIndex(CTxMemPool& mempool, CSpentIndexKey& key, CSpentIndexValue& value)
+bool GetSpentIndex(const CTxMemPool& mempool, CSpentIndexKey& key, CSpentIndexValue& value)
 {
     if (!fSpentIndex)
         return false;
diff --git a/src/rpc/index_util.h b/src/rpc/index_util.h
index af01cadf9c..15b82eb2a5 100644
--- a/src/rpc/index_util.h
+++ b/src/rpc/index_util.h
@@ -27,7 +27,7 @@ bool GetAddressIndex(uint160 addressHash, AddressType type,
                      int32_t start = 0, int32_t end = 0);
 bool GetAddressUnspentIndex(uint160 addressHash, AddressType type,
                             std::vector<std::pair<CAddressUnspentKey, CAddressUnspentValue>>& unspentOutputs);
-bool GetSpentIndex(CTxMemPool& mempool, CSpentIndexKey& key, CSpentIndexValue& value);
+bool GetSpentIndex(const CTxMemPool& mempool, CSpentIndexKey& key, CSpentIndexValue& value);
 bool GetTimestampIndex(const uint32_t high, const uint32_t low, std::vector<uint256>& hashes);
 
 #endif // BITCOIN_RPC_CLIENT_H
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index a9b9a09360..a2eaf621ff 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -427,7 +427,7 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
     }
 }
 
-void CTxMemPool::addAddressIndex(const CTxMemPoolEntry &entry, const CCoinsViewCache &view)
+void CTxMemPool::addAddressIndex(const CTxMemPoolEntry& entry, const CCoinsViewCache& view)
 {
     LOCK(cs);
     const CTransaction& tx = entry.GetTx();
@@ -470,12 +470,12 @@ void CTxMemPool::addAddressIndex(const CTxMemPoolEntry &entry, const CCoinsViewC
     mapAddressInserted.insert(std::make_pair(txhash, inserted));
 }
 
-bool CTxMemPool::getAddressIndex(std::vector<std::pair<uint160, AddressType> > &addresses,
-                                 std::vector<std::pair<CMempoolAddressDeltaKey, CMempoolAddressDelta> > &results)
+bool CTxMemPool::getAddressIndex(const std::vector<std::pair<uint160, AddressType>>& addresses,
+                                 std::vector<std::pair<CMempoolAddressDeltaKey, CMempoolAddressDelta>>& results) const
 {
     LOCK(cs);
     for (const auto& address : addresses) {
-        addressDeltaMap::iterator ait = mapAddress.lower_bound(CMempoolAddressDeltaKey(address.second, address.first));
+        addressDeltaMap::const_iterator ait = mapAddress.lower_bound(CMempoolAddressDeltaKey(address.second, address.first));
         while (ait != mapAddress.end() && (*ait).first.m_address_bytes == address.first && (*ait).first.m_address_type == address.second) {
             results.push_back(*ait);
             ait++;
@@ -500,7 +500,7 @@ bool CTxMemPool::removeAddressIndex(const uint256 txhash)
     return true;
 }
 
-void CTxMemPool::addSpentIndex(const CTxMemPoolEntry &entry, const CCoinsViewCache &view)
+void CTxMemPool::addSpentIndex(const CTxMemPoolEntry& entry, const CCoinsViewCache& view)
 {
     LOCK(cs);
 
@@ -530,12 +530,11 @@ void CTxMemPool::addSpentIndex(const CTxMemPoolEntry &entry, const CCoinsViewCac
     mapSpentInserted.insert(make_pair(txhash, inserted));
 }
 
-bool CTxMemPool::getSpentIndex(CSpentIndexKey &key, CSpentIndexValue &value)
+bool CTxMemPool::getSpentIndex(const CSpentIndexKey& key, CSpentIndexValue& value) const
 {
     LOCK(cs);
-    mapSpentIndex::iterator it;
+    mapSpentIndex::const_iterator it = mapSpent.find(key);
 
-    it = mapSpent.find(key);
     if (it != mapSpent.end()) {
         value = it->second;
         return true;
diff --git a/src/txmempool.h b/src/txmempool.h
index a4717b7e88..823b45e892 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -635,13 +635,13 @@ public:
     void addUnchecked(const CTxMemPoolEntry& entry, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
     void addUnchecked(const CTxMemPoolEntry& entry, setEntries& setAncestors, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
 
-    void addAddressIndex(const CTxMemPoolEntry &entry, const CCoinsViewCache &view);
-    bool getAddressIndex(std::vector<std::pair<uint160, AddressType> > &addresses,
-                         std::vector<std::pair<CMempoolAddressDeltaKey, CMempoolAddressDelta> > &results);
+    void addAddressIndex(const CTxMemPoolEntry& entry, const CCoinsViewCache& view);
+    bool getAddressIndex(const std::vector<std::pair<uint160, AddressType>>& addresses,
+                         std::vector<std::pair<CMempoolAddressDeltaKey, CMempoolAddressDelta>>& results) const;
     bool removeAddressIndex(const uint256 txhash);
 
-    void addSpentIndex(const CTxMemPoolEntry &entry, const CCoinsViewCache &view);
-    bool getSpentIndex(CSpentIndexKey &key, CSpentIndexValue &value);
+    void addSpentIndex(const CTxMemPoolEntry& entry, const CCoinsViewCache& view);
+    bool getSpentIndex(const CSpentIndexKey& key, CSpentIndexValue& value) const;
     bool removeSpentIndex(const uint256 txhash);
 
     void removeRecursive(const CTransaction& tx, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);