Gazprom and Naftogaz had signed a technical agreement on the transit of gas.

"Gazprom and Naftogaz of Ukraine signed a technical agreement on the transit of Russian gas through Ukraine. That was reported by RIA Novosti. The agreement was signed for a year, but may be extended until the end of the contract for the supply of gas, that is, until 2019.
The draft agreement was prepared during the January conflict around the transit of Russian gas through Ukraine to Europe. It set out areas of the transit of gas, the properties of the supplied fuel, as well as the pressure at the inlet and outlet of the Ukrainian GTS.
According to the Interfax, Ukrainian experts pointed out that the absence of this document is an obstacle to the implementation of the current Russian-Ukrainian contracts.
Gas conflict between Gazprom and Naftogaz "appeared in January 2009 due to lack of contracts for the supply of gas. During the crisis, the transit of Russian gas through Ukrainian territory was almost completely stopped for two weeks. Later, the parties managed to agree on contracts for the supply of gas.
In late March, Ukraine and the EU signed in Brussels an agreement on the modernization of the Ukrainian GTS. This paper, in particular, provides the access of European companies to the Ukrainian underground storage facilities and pipes. The Declaration has been prepared without the participation of the Russian side, which caused a number of critical comments made by officials of Russia, as well as top management of Gazprom.