This looks like an irregular verb. If спати is the infinitive I was expecting something like спю.
I'm not sure if this is considered irregular, but many verbs with stem ending in -п-, -б-, -в- get л in 1st person singular and 3rd person plural:
- люби́ти 'to like': я люблю́ 'I like', вони лю́блять 'they like',
- ліпи́ти 'to model (e.g. out of clay); to stick, to paste': я ліплю́ 'I model', вони́ лíплять 'they model',
- си́пати 'to pour (a dry substance)': я си́плю 'I scatter, I pour (e.g. salt)', вони́ си́плять 'they scatter',
- купи́ти 'to buy': я куплю́ 'I will buy', вони́ ку́плять 'they will buy' (it's in future because it's a perfective verb and doesn't have a present tense form, while other examples are imperfective),
- роби́ти 'to do, to make': я роблю́ 'I do, I make', вони́ ро́блять 'they do, they make',
- дави́ти 'to press, to squeeze; to oppress': я давлю́ 'I press', вони́ да́влять 'they press'.
(NB. I've marked the stress according to the dictionary. However, I personally pronounce some forms differently: я лю́блю, я лíплю, я ку́плю, я ро́блю, я да́влю. I think the stress I use is not uncommon, at least I tend to hear it a lot.)