diff --git a/src/keystore.h b/src/keystore.h
--- a/src/keystore.h
+++ b/src/keystore.h
@@ -30,7 +30,7 @@
     //! store.
     virtual bool HaveKey(const CKeyID &address) const = 0;
     virtual bool GetKey(const CKeyID &address, CKey &keyOut) const = 0;
-    virtual void GetKeys(std::set<CKeyID> &setAddress) const = 0;
+    virtual std::set<CKeyID> GetKeys() const = 0;
     virtual bool GetPubKey(const CKeyID &address,
                            CPubKey &vchPubKeyOut) const = 0;
 
@@ -72,16 +72,13 @@
         }
         return result;
     }
-    void GetKeys(std::set<CKeyID> &setAddress) const override {
-        setAddress.clear();
-        {
-            LOCK(cs_KeyStore);
-            KeyMap::const_iterator mi = mapKeys.begin();
-            while (mi != mapKeys.end()) {
-                setAddress.insert((*mi).first);
-                mi++;
-            }
+    std::set<CKeyID> GetKeys() const override {
+        LOCK(cs_KeyStore);
+        std::set<CKeyID> set_address;
+        for (const auto &mi : mapKeys) {
+            set_address.insert(mi.first);
         }
+        return set_address;
     }
     bool GetKey(const CKeyID &address, CKey &keyOut) const override {
         {
diff --git a/src/wallet/crypter.h b/src/wallet/crypter.h
--- a/src/wallet/crypter.h
+++ b/src/wallet/crypter.h
@@ -165,17 +165,16 @@
     }
     bool GetKey(const CKeyID &address, CKey &keyOut) const override;
     bool GetPubKey(const CKeyID &address, CPubKey &vchPubKeyOut) const override;
-    void GetKeys(std::set<CKeyID> &setAddress) const override {
+    std::set<CKeyID> GetKeys() const override {
+        LOCK(cs_KeyStore);
         if (!IsCrypted()) {
-            CBasicKeyStore::GetKeys(setAddress);
-            return;
+            return CBasicKeyStore::GetKeys();
         }
-        setAddress.clear();
-        CryptedKeyMap::const_iterator mi = mapCryptedKeys.begin();
-        while (mi != mapCryptedKeys.end()) {
-            setAddress.insert((*mi).first);
-            mi++;
+        std::set<CKeyID> set_address;
+        for (const auto &mi : mapCryptedKeys) {
+            set_address.insert(mi.first);
         }
+        return set_address;
     }
 
     /**
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3811,14 +3811,11 @@
     CBlockIndex *pindexMax =
         chainActive[std::max(0, chainActive.Height() - 144)];
     std::map<CKeyID, CBlockIndex *> mapKeyFirstBlock;
-    std::set<CKeyID> setKeys;
-    GetKeys(setKeys);
-    for (const CKeyID &keyid : setKeys) {
+    for (const CKeyID &keyid : GetKeys()) {
         if (mapKeyBirth.count(keyid) == 0) {
             mapKeyFirstBlock[keyid] = pindexMax;
         }
     }
-    setKeys.clear();
 
     // If there are no such keys, we're done.
     if (mapKeyFirstBlock.empty()) {