We went down in 4 Hearts. Everyone else bid and made 4 spades. Partner had two small spades.
My rationale was that by a jump rebid I was showing six spades, and partner's first bid showed 5+ hearts and his second bid showed 6 hearts. I assumed he could not have two spades or he would have put me into game in spades with an 8 card fit, and he might have a void in spades, so I might struggle to get to his hand to establish his Hearts with only a singleton ♥Q in my hand. On the other hand, in 4 Hearts, if partner was very short in spades he would be relying on a successful Club King finesse to run my spades.
Should partner have put me into game in Spades with an 8 card fit, or were my spades solid enough for me to bid over his 4 Hearts?