By analysing natural gas as a transitional fuel to renewables in the EU-Russian discourse, this article addresses energy cooperation in the International Gas Union (IGU) and geopolitics of energy transition within the International Renewable Energy Agency (IRENA). The understanding of the institutional setting is based on a constructivist approach. It is argued that the structure of the international organisation influences the rules of the game and the behaviour of the actors can be anticipated within the structure. Thus, sovereignty and geopolitical debates prevail in the intergovernmental institution, while a market-oriented discourse dominates in the non-governmental organisation. Nord Stream 2 is used as a case to test the impact of the norms “gas as a back-up fuel” for renewables and “reliability of supply” in the energy transition debate.