diff --git a/lib/chibi/math/prime.scm b/lib/chibi/math/prime.scm
index 701d1ef7..65ba56e3 100644
--- a/lib/chibi/math/prime.scm
+++ b/lib/chibi/math/prime.scm
@@ -171,15 +171,14 @@
     (list n))
    (else
     (let lp ((n n)
-             (limit (exact (ceiling (sqrt n))))
              (res (list)))
       (cond
        ((even? n)
-        (lp (quotient n 2) (quotient limit 2) (cons 2 res)))
+        (lp (quotient n 2) (cons 2 res)))
        ((= n 1)
         (reverse res))
        (else
-        (let lp ((i 3) (n n) (limit limit) (res res))
+        (let lp ((i 3) (n n) (limit (exact (ceiling (sqrt n)))) (res res))
           (cond
            ((= n 1)
             (reverse res))
diff --git a/tests/prime-tests.scm b/tests/prime-tests.scm
index 540c3ab0..a060f82c 100644
--- a/tests/prime-tests.scm
+++ b/tests/prime-tests.scm
@@ -68,6 +68,8 @@
 (test '(2 5) (factor 10))
 (test '(11) (factor 11))
 (test '(2 2 3) (factor 12))
+(test '(2 3 3) (factor 18))
+(test '(2 2 2 3 3) (factor 72))
 (test '(3 3 3 5 7) (factor 945))
 
 (test 975 (aliquot 945))