Why is emissions light back on your corsa?

I know this sounds surprising, had an issue with the Opel Corsa C equivalent, a 2002 Holden Barina SRi. The emission light came on after a stall and stayed on. It was just after a re-fill of the petrol tank. I turned off the engine, removed the petrol cap and re-sealed it and the light went off and has stayed off.

Hope this helps.