diff --git a/src/hooks/dhcp/lease_cmds/lease_cmds.cc b/src/hooks/dhcp/lease_cmds/lease_cmds.cc
index 14d1f3ab4a..c78e8e1cdc 100644
--- a/src/hooks/dhcp/lease_cmds/lease_cmds.cc
+++ b/src/hooks/dhcp/lease_cmds/lease_cmds.cc
@@ -1125,7 +1125,7 @@ LeaseCmdsImpl::lease6BulkApplyHandler(CalloutHandle& handle) {
                 // Parsing the lease may throw and it means that the lease
                 // information is malformed.
                 Parameters p = getParameters(true, lease_params);
-                auto lease = getIPv6AddressForDelete(p);
+                auto lease = getIPv6LeaseForDelete(p);
                 parsed_deleted_list.push_back(std::make_pair(p, lease));
             }
         }
diff --git a/src/lib/dhcpsrv/mysql_lease_mgr.cc b/src/lib/dhcpsrv/mysql_lease_mgr.cc
index 2ec44e818c..465201ca30 100644
--- a/src/lib/dhcpsrv/mysql_lease_mgr.cc
+++ b/src/lib/dhcpsrv/mysql_lease_mgr.cc
@@ -615,7 +615,7 @@ public:
             ConstElementPtr ctx = lease->getContext();
             if (ctx) {
                 bind_[10].buffer_type = MYSQL_TYPE_STRING;
-                string ctx_txt = ctx->str();
+                std::string ctx_txt = ctx->str();
                 strncpy(user_context_, ctx_txt.c_str(), USER_CONTEXT_MAX_LEN - 1);
                 bind_[10].buffer = user_context_;
                 bind_[10].buffer_length = ctx_txt.length();
@@ -1158,7 +1158,7 @@ public:
             ConstElementPtr ctx = lease->getContext();
             if (ctx) {
                 bind_[16].buffer_type = MYSQL_TYPE_STRING;
-                string ctx_txt = ctx->str();
+                std::string ctx_txt = ctx->str();
                 strncpy(user_context_, ctx_txt.c_str(), USER_CONTEXT_MAX_LEN - 1);
                 bind_[16].buffer = user_context_;
                 bind_[16].buffer_length = ctx_txt.length();
@@ -2254,7 +2254,7 @@ MySqlLeaseMgr::getLeases4(SubnetID subnet_id) const {
 }
 
 Lease4Collection
-MySqlLeaseMgr::getLeases4(const string& hostname) const {
+MySqlLeaseMgr::getLeases4(const std::string& hostname) const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL, DHCPSRV_MYSQL_GET_HOSTNAME4)
         .arg(hostname);
 
@@ -2557,7 +2557,7 @@ MySqlLeaseMgr::getLeases6(const DUID& duid) const {
 }
 
 Lease6Collection
-MySqlLeaseMgr::getLeases6(const string& hostname) const {
+MySqlLeaseMgr::getLeases6(const std::string& hostname) const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL, DHCPSRV_MYSQL_GET_HOSTNAME6)
         .arg(hostname);
 
diff --git a/src/lib/dhcpsrv/pgsql_lease_mgr.cc b/src/lib/dhcpsrv/pgsql_lease_mgr.cc
index a63830bfac..0a7aeef7ab 100644
--- a/src/lib/dhcpsrv/pgsql_lease_mgr.cc
+++ b/src/lib/dhcpsrv/pgsql_lease_mgr.cc
@@ -29,6 +29,7 @@ using namespace isc::db;
 using namespace isc::dhcp;
 using namespace isc::data;
 using namespace isc::util;
+using namespace std;
 
 namespace {
 
@@ -1546,7 +1547,7 @@ PgSqlLeaseMgr::getLeases4(SubnetID subnet_id) const {
 }
 
 Lease4Collection
-PgSqlLeaseMgr::getLeases4(const string& hostname) const {
+PgSqlLeaseMgr::getLeases4(const std::string& hostname) const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL, DHCPSRV_PGSQL_GET_HOSTNAME4)
         .arg(hostname);
 
@@ -1773,7 +1774,7 @@ PgSqlLeaseMgr::getLeases6(const DUID& duid) const {
 }
 
 Lease6Collection
-PgSqlLeaseMgr::getLeases6(const string& hostname) const {
+PgSqlLeaseMgr::getLeases6(const std::string& hostname) const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL, DHCPSRV_PGSQL_GET_HOSTNAME6)
         .arg(hostname);
 
@@ -2182,13 +2183,13 @@ PgSqlLeaseMgr::wipeLeases6(const SubnetID& /*subnet_id*/) {
     isc_throw(NotImplemented, "wipeLeases6 is not implemented for PostgreSQL backend");
 }
 
-string
+std::string
 PgSqlLeaseMgr::getName() const {
     // Get a context
     PgSqlLeaseContextAlloc get_context(*this);
     PgSqlLeaseContextPtr ctx = get_context.ctx_;
 
-    string name = "";
+    std::string name = "";
     try {
         name = ctx->conn_.getParameter("name");
     } catch (...) {
@@ -2197,12 +2198,12 @@ PgSqlLeaseMgr::getName() const {
     return (name);
 }
 
-string
+std::string
 PgSqlLeaseMgr::getDescription() const {
-    return (string("PostgreSQL Database"));
+    return (std::string("PostgreSQL Database"));
 }
 
-pair<uint32_t, uint32_t>
+std::pair<uint32_t, uint32_t>
 PgSqlLeaseMgr::getVersion() const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL, DHCPSRV_PGSQL_GET_VERSION);