diff --git a/src/CallRPC.cpp b/src/CallRPC.cpp
index 50896b858..a8337198e 100644
--- a/src/CallRPC.cpp
+++ b/src/CallRPC.cpp
@@ -36,7 +36,7 @@ std::string EncodeBase64(const std::string& s)
 	BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
 	bmem = BIO_new(BIO_s_mem());
 	b64 = BIO_push(b64, bmem);
-	BIO_write(b64, s.c_str(), s.size());
+	BIO_write(b64, s.data(), s.size());
 	(void) BIO_flush(b64);
 	BIO_get_mem_ptr(b64, &bptr);
 
diff --git a/src/DeterministicKeys.cpp b/src/DeterministicKeys.cpp
index 1f1e1a0c9..622c98598 100644
--- a/src/DeterministicKeys.cpp
+++ b/src/DeterministicKeys.cpp
@@ -19,7 +19,7 @@ uint128 CKey::PassPhraseToKey(const std::string& passPhrase)
 {
 	Serializer s;
 
-	s.addRaw(passPhrase.c_str(), passPhrase.size());
+	s.addRaw(passPhrase);
 	uint256	hash256	= s.getSHA512Half();
 	uint128 ret(hash256);
 
diff --git a/src/RPCHandler.cpp b/src/RPCHandler.cpp
index 36fcfdffd..dbb6eb542 100644
--- a/src/RPCHandler.cpp
+++ b/src/RPCHandler.cpp
@@ -411,7 +411,7 @@ Json::Value RPCHandler::doAccountEmailSet(const Json::Value &params)
 	boost::to_lower(strEmail);
 
 	std::vector<unsigned char>	vucMD5(128/8, 0);
-	MD5(reinterpret_cast<const unsigned char*>(strEmail.c_str()), strEmail.size(), &vucMD5.front());
+	MD5(reinterpret_cast<const unsigned char*>(strEmail.data()), strEmail.size(), &vucMD5.front());
 
 	uint128						uEmailHash(vucMD5);
 	std::vector<unsigned char>	vucDomain;
diff --git a/src/rpc.cpp b/src/rpc.cpp
index 15f53061c..2beec4c66 100644
--- a/src/rpc.cpp
+++ b/src/rpc.cpp
@@ -189,7 +189,7 @@ std::string DecodeBase64(std::string s)
 
 	b64 = BIO_new(BIO_f_base64());
 	BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
-	bmem = BIO_new_mem_buf(const_cast<char*>(s.c_str()), s.size());
+	bmem = BIO_new_mem_buf(const_cast<char*>(s.data()), s.size());
 	bmem = BIO_push(b64, bmem);
 	BIO_read(bmem, buffer, s.size());
 	BIO_free_all(bmem);