diff --git a/src/lib/dhcpsrv/memfile_lease_mgr.cc b/src/lib/dhcpsrv/memfile_lease_mgr.cc
index 713d6257f983c10267e2c000a3ecf542b5ad6b7f..804eef86c5a588b97d70d3345b087217422ed452 100644
--- a/src/lib/dhcpsrv/memfile_lease_mgr.cc
+++ b/src/lib/dhcpsrv/memfile_lease_mgr.cc
@@ -62,7 +62,7 @@ Lease4Ptr Memfile_LeaseMgr::getLease4(const isc::asiolink::IOAddress& addr) cons
     if (l == storage4_.end()) {
         return (Lease4Ptr());
     } else {
-        return (*l);
+        return (Lease4Ptr(new Lease4(**l)));
     }
 }
 
@@ -94,7 +94,7 @@ Lease4Ptr Memfile_LeaseMgr::getLease4(const HWAddr& hwaddr,
     }
 
     // Lease was found. Return it to the caller.
-    return (*lease);
+    return (Lease4Ptr(new Lease4(**lease)));
 }
 
 Lease4Collection Memfile_LeaseMgr::getLease4(const ClientId& clientid) const {
@@ -123,11 +123,11 @@ Lease4Ptr Memfile_LeaseMgr::getLease4(const ClientId& client_id,
         return Lease4Ptr();
     }
     // Lease was found. Return it to the caller.
-    return (*lease);
+    return (Lease4Ptr(new Lease4(**lease)));
 }
 
-Lease6Ptr Memfile_LeaseMgr::getLease6(
-        const isc::asiolink::IOAddress& addr) const {
+Lease6Ptr
+Memfile_LeaseMgr::getLease6(const isc::asiolink::IOAddress& addr) const {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL,
               DHCPSRV_MEMFILE_GET_ADDR6).arg(addr.toText());
 
@@ -135,7 +135,7 @@ Lease6Ptr Memfile_LeaseMgr::getLease6(
     if (l == storage6_.end()) {
         return (Lease6Ptr());
     } else {
-        return (*l);
+        return (Lease6Ptr(new Lease6(**l)));
     }
 }
 
@@ -167,20 +167,31 @@ Lease6Ptr Memfile_LeaseMgr::getLease6(const DUID& duid, uint32_t iaid,
         return (Lease6Ptr());
     }
     // Lease was found, return it to the caller.
-    return (*lease);
+    return (Lease6Ptr(new Lease6(**lease)));
 }
 
 void Memfile_LeaseMgr::updateLease4(const Lease4Ptr& lease) {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL,
               DHCPSRV_MEMFILE_UPDATE_ADDR4).arg(lease->addr_.toText());
 
+    Lease4Storage::iterator lease_it = storage4_.find(lease->addr_);
+    if (lease_it == storage4_.end()) {
+        isc_throw(NoSuchLease, "failed to update the lease with address "
+                  << lease->addr_.toText() << " - no such lease");
+    }
+    **lease_it = *lease;
 }
 
 void Memfile_LeaseMgr::updateLease6(const Lease6Ptr& lease) {
     LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE_DETAIL,
               DHCPSRV_MEMFILE_UPDATE_ADDR6).arg(lease->addr_.toText());
 
-
+    Lease6Storage::iterator lease_it = storage6_.find(lease->addr_);
+    if (lease_it == storage6_.end()) {
+        isc_throw(NoSuchLease, "failed to update the lease with address "
+                  << lease->addr_.toText() << " - no such lease");
+    }
+    **lease_it = *lease;
 }
 
 bool Memfile_LeaseMgr::deleteLease(const isc::asiolink::IOAddress& addr) {
diff --git a/src/lib/dhcpsrv/memfile_lease_mgr.h b/src/lib/dhcpsrv/memfile_lease_mgr.h
index 4ac753650f1c88804db42c7e1292dc0735451d92..2f75a98067d84c4126bfe13bd32b4c90b55cd29d 100644
--- a/src/lib/dhcpsrv/memfile_lease_mgr.h
+++ b/src/lib/dhcpsrv/memfile_lease_mgr.h
@@ -65,8 +65,10 @@ public:
 
     /// @brief Returns existing IPv4 lease for specified IPv4 address.
     ///
-    /// @todo Not implemented yet
-    /// @param addr address of the searched lease
+    /// This function returns a copy of the lease. The modification in the
+    /// return lease does not affect the instance held in the lease storage.
+    ///
+    /// @param addr An address of the searched lease.
     ///
     /// @return a collection of leases
     virtual Lease4Ptr getLease4(const isc::asiolink::IOAddress& addr) const;
@@ -85,10 +87,11 @@ public:
     /// @return lease collection
     virtual Lease4Collection getLease4(const isc::dhcp::HWAddr& hwaddr) const;
 
-    /// @brief Returns existing IPv4 leases for specified hardware address
+    /// @brief Returns existing IPv4 lease for specified hardware address
     ///        and a subnet
     ///
-    /// @todo Not implemented yet
+    /// This function returns a copy of the lease. The modification in the
+    /// return lease does not affect the instance held in the lease storage.
     ///
     /// There can be at most one lease for a given HW address in a single
     /// pool, so this method with either return a single lease or NULL.
@@ -109,11 +112,12 @@ public:
 
     /// @brief Returns existing IPv4 lease for specified client-id
     ///
+    /// This function returns a copy of the lease. The modification in the
+    /// return lease does not affect the instance held in the lease storage.
+    ///
     /// There can be at most one lease for a given HW address in a single
     /// pool, so this method with either return a single lease or NULL.
     ///
-    /// @todo Not implemented yet
-    ///
     /// @param clientid client identifier
     /// @param subnet_id identifier of the subnet that lease must belong to
     ///
@@ -123,7 +127,10 @@ public:
 
     /// @brief Returns existing IPv6 lease for a given IPv6 address.
     ///
-    /// @param addr address of the searched lease
+    /// This function returns a copy of the lease. The modification in the
+    /// return lease does not affect the instance held in the lease storage.
+    ///
+    /// @param addr An address of the searched lease.
     ///
     /// @return smart pointer to the lease (or NULL if a lease is not found)
     virtual Lease6Ptr getLease6(const isc::asiolink::IOAddress& addr) const;
@@ -140,27 +147,31 @@ public:
 
     /// @brief Returns existing IPv6 lease for a given DUID+IA combination
     ///
-    /// @todo Not implemented yet
+    /// This function returns a copy of the lease. The modification in the
+    /// return lease does not affect the instance held in the lease storage.
     ///
     /// @param duid client DUID
     /// @param iaid IA identifier
     /// @param subnet_id identifier of the subnet the lease must belong to
     ///
     /// @return smart pointer to the lease (or NULL if a lease is not found)
-    virtual Lease6Ptr getLease6(const DUID& duid, uint32_t iaid, SubnetID subnet_id) const;
+    virtual Lease6Ptr getLease6(const DUID& duid, uint32_t iaid,
+                                SubnetID subnet_id) const;
 
     /// @brief Updates IPv4 lease.
     ///
-    /// @todo Not implemented yet
+    /// @warning This function does not validate the pointer to the lease.
+    /// It is caller's responsibility to pass the valid pointer.
     ///
     /// @param lease4 The lease to be updated.
     ///
     /// If no such lease is present, an exception will be thrown.
     virtual void updateLease4(const Lease4Ptr& lease4);
 
-    /// @brief Updates IPv4 lease.
+    /// @brief Updates IPv6 lease.
     ///
-    /// @todo Not implemented yet
+    /// @warning This function does not validate the pointer to the lease.
+    /// It is caller's responsibility to pass the valid pointer.
     ///
     /// @param lease6 The lease to be updated.
     ///