diff --git a/collects/scribblings/reference/numbers.scrbl b/collects/scribblings/reference/numbers.scrbl
index 41ad7d2d21..e2f4e2ff4d 100644
--- a/collects/scribblings/reference/numbers.scrbl
+++ b/collects/scribblings/reference/numbers.scrbl
@@ -594,13 +594,13 @@ In the one-argument case, returns the arctangent of the inexact
  approximation of @racket[z], except that the result is an exact
  @racket[0] for an exact @racket[0] argument.
 
-In the two-argument case, the result is roughly the same as @racket[(/
- (exact->inexact y) (exact->inexact x))], but the signs of @racket[y]
+In the two-argument case, the result is roughly the same as @racket[
+ (atan (/ (exact->inexact y)) (exact->inexact x))], but the signs of @racket[y]
  and @racket[x] determine the quadrant of the result. Moreover, a
  suitable angle is returned when @racket[y] divided by @racket[x]
  produces @racket[+nan.0] in the case that neither @racket[y] nor
- @racket[x] is @racket[+nan.0]. Finally, if @racket[x] is exact
- @racket[0] and @racket[y] is an exact positive number, the result is
+ @racket[x] is @racket[+nan.0]. Finally, if @racket[y] is exact
+ @racket[0] and @racket[x] is an exact positive number, the result is
  exact @racket[0]. If both @racket[x] and @racket[y] are exact
  @racket[0], the @exnraise[exn:fail:contract:divide-by-zero].
 
diff --git a/collects/tests/racket/number.rktl b/collects/tests/racket/number.rktl
index 4159d18488..7c55c1ec93 100644
--- a/collects/tests/racket/number.rktl
+++ b/collects/tests/racket/number.rktl
@@ -1843,6 +1843,7 @@
 (test 0.0 atan 0.0 0)
 (test 0 atan 0 1)
 (test 0 atan 0 (expt 2 100))
+(test 0 atan 0 5/2)
 (test 0.0 atan 0 1.0)
 (test 314.0 round (* 100 (atan 0 -1)))
 (err/rt-test (atan 0 0) exn:fail:contract:divide-by-zero?)
diff --git a/src/racket/src/number.c b/src/racket/src/number.c
index 5540cd7020..a4cb69b725 100644
--- a/src/racket/src/number.c
+++ b/src/racket/src/number.c
@@ -2243,7 +2243,8 @@ atan_prim (int argc, Scheme_Object *argv[])
         ESCAPED_BEFORE_HERE;
       }
       if ((SCHEME_INTP(n2) && (SCHEME_INT_VAL(n2) > 0))
-          || (SCHEME_BIGNUMP(n2) && (SCHEME_BIGPOS(n2))))
+          || (SCHEME_BIGNUMP(n2) && (SCHEME_BIGPOS(n2)))
+          || (SCHEME_RATIONALP(n2) && scheme_is_positive(n2)))
         return zeroi;
     }