diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index 36946b7dc..53cfcf096 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -148,7 +148,7 @@ void CDBEnv::MakeMock()
     fMockDb = true;
 }
 
-CDBEnv::VerifyResult CDBEnv::Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile))
+CDBEnv::VerifyResult CDBEnv::Verify(const std::string& strFile, bool (*recoverFunc)(CDBEnv& dbenv, const std::string& strFile))
 {
     LOCK(cs_db);
     assert(mapFileUseCount.count(strFile) == 0);
@@ -165,7 +165,7 @@ CDBEnv::VerifyResult CDBEnv::Verify(std::string strFile, bool (*recoverFunc)(CDB
     return (fRecovered ? RECOVER_OK : RECOVER_FAIL);
 }
 
-bool CDBEnv::Salvage(std::string strFile, bool fAggressive, std::vector<CDBEnv::KeyValPair>& vResult)
+bool CDBEnv::Salvage(const std::string& strFile, bool fAggressive, std::vector<CDBEnv::KeyValPair>& vResult)
 {
     LOCK(cs_db);
     assert(mapFileUseCount.count(strFile) == 0);
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 71133f969..0c2c139d8 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -59,7 +59,7 @@ public:
     enum VerifyResult { VERIFY_OK,
                         RECOVER_OK,
                         RECOVER_FAIL };
-    VerifyResult Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile));
+    VerifyResult Verify(const std::string& strFile, bool (*recoverFunc)(CDBEnv& dbenv, const std::string& strFile));
     /**
      * Salvage data from a file that Verify says is bad.
      * fAggressive sets the DB_AGGRESSIVE flag (see berkeley DB->verify() method documentation).
@@ -68,7 +68,7 @@ public:
      * for huge databases.
      */
     typedef std::pair<std::vector<unsigned char>, std::vector<unsigned char> > KeyValPair;
-    bool Salvage(std::string strFile, bool fAggressive, std::vector<KeyValPair>& vResult);
+    bool Salvage(const std::string& strFile, bool fAggressive, std::vector<KeyValPair>& vResult);
 
     bool Open(const boost::filesystem::path& path);
     void Close();
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 44b416d49..167639b53 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -345,7 +345,7 @@ void CWallet::Flush(bool shutdown)
     bitdb.Flush(shutdown);
 }
 
-bool CWallet::Verify(const string walletFile, string& warningString, string& errorString)
+bool CWallet::Verify(const string& walletFile, string& warningString, string& errorString)
 {
     if (!bitdb.Open(GetDataDir()))
     {
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 1a9feff9f..f00fb0caf 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -747,7 +747,7 @@ public:
     void Flush(bool shutdown=false);
 
     //! Verify the wallet database and perform salvage if required
-    static bool Verify(const std::string walletFile, std::string& warningString, std::string& errorString);
+    static bool Verify(const std::string& walletFile, std::string& warningString, std::string& errorString);
     
     /** 
      * Address book entry changed.
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 880026d18..d7f70e435 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -891,7 +891,7 @@ bool BackupWallet(const CWallet& wallet, const string& strDest)
 //
 // Try to (very carefully!) recover wallet.dat if there is a problem.
 //
-bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys)
+bool CWalletDB::Recover(CDBEnv& dbenv, const std::string& filename, bool fOnlyKeys)
 {
     // Recovery procedure:
     // move wallet.dat to wallet.timestamp.bak
@@ -968,7 +968,7 @@ bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys)
     return fSuccess;
 }
 
-bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename)
+bool CWalletDB::Recover(CDBEnv& dbenv, const std::string& filename)
 {
     return CWalletDB::Recover(dbenv, filename, false);
 }
diff --git a/src/wallet/walletdb.h b/src/wallet/walletdb.h
index 6aa0fa40d..a1c38b9d3 100644
--- a/src/wallet/walletdb.h
+++ b/src/wallet/walletdb.h
@@ -127,8 +127,8 @@ public:
     DBErrors LoadWallet(CWallet* pwallet);
     DBErrors FindWalletTx(CWallet* pwallet, std::vector<uint256>& vTxHash, std::vector<CWalletTx>& vWtx);
     DBErrors ZapWalletTx(CWallet* pwallet, std::vector<CWalletTx>& vWtx);
-    static bool Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys);
-    static bool Recover(CDBEnv& dbenv, std::string filename);
+    static bool Recover(CDBEnv& dbenv, const std::string& filename, bool fOnlyKeys);
+    static bool Recover(CDBEnv& dbenv, const std::string& filename);
 
 private:
     CWalletDB(const CWalletDB&);