Dear guile, The following program should just return 'foo, but it enters an infinite loop: (use-modules (oop goops)) (define-class ()) (define-method (no-method (generic ) args) 'foo) (define-method (no-applicable-method (generic ) args) 'foo) (define hello (make #:name 'hello)) (hello) I don’t know GOOPS enough to understand what happens, but when I slightly change the last line: (use-modules (oop goops)) (define-class ()) (define-method (no-method (generic ) args) 'foo) (define-method (no-applicable-method (generic ) args) 'foo) (define hello (make #:name 'hello)) (apply-generic hello '()) Now it returns 'foo, as expected. So my guess is that the infinite loops happens during the memoization phase. More specifically, the no- applicable-method is called over and over again. Please find a failing test case attached. Best regards, Vivien