The invention provides a crystalline hydrochloride salt of 1-isopropyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid {(1S,3R,5R)-8-[(R)-2-hydroxy-3-(methanesulfonyl-methyl-amino)propyl]-8-azabicyclo[3.2.1]oct-3-yl}amide or a solvate thereof. The invention also provides pharmaceutical compositions comprising such crystalline salt forms, methods of using such crystalline salt forms to treat diseases associated with 5-HT4 receptor activity, and processes useful for preparing such crystalline salt forms.