slime-edit-definition doesn't lookup the definition at point

In my Lisp buffer, when the point is over a symbol and I press M-. (slime-edit-definition), I get the following error: cl-assoc: Symbol's function definition is void: equalp If the point is over some whitespace, then things work as expected: M-. gives me the "Edit Definition of" prompt in the minibuffer and looks up the correct definition. I guess I can define equalp in my .emacs to fix this, but I would prefer if it worked out of the box. I am using GNU Emacs 24.5.1 and SLIME 20160624.851 (installed from melpa). Chaitanya