diff --git a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
index a928830f38..cd0ca4bccf 100644
--- a/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
+++ b/collects/tests/typed-racket/unit-tests/typecheck-tests.rkt
@@ -28,7 +28,7 @@
                      (typecheck typechecker)
                      (env global-env)
                      (base-env base-env-indexing))
-         racket/file racket/port racket/flonum
+         racket/file racket/port racket/flonum racket/math
          (env global-env)
          (for-meta 2 (env global-env))
          (for-template
@@ -225,6 +225,7 @@
         (tc-e (flexpt 0.5 0.3) -NonNegFlonum)
         (tc-e (flexpt 0.00000000001 100000000000.0) -NonNegFlonum)
         (tc-e (flexpt -2.0 -0.5) -Flonum) ; NaN
+        (tc-e (tanh (ann 0 Nonnegative-Integer)) -NonNegReal)
         (tc-e (angle -1) -Real)
         (tc-e (angle 2.3) -Zero)
         (tc-e (magnitude 3/4) -PosRat)
diff --git a/collects/typed-racket/base-env/base-env-numeric.rkt b/collects/typed-racket/base-env/base-env-numeric.rkt
index b4de39ea74..095dd629ab 100644
--- a/collects/typed-racket/base-env/base-env-numeric.rkt
+++ b/collects/typed-racket/base-env/base-env-numeric.rkt
@@ -1908,8 +1908,9 @@
        (map unop (list -FloatComplex -SingleFlonumComplex -InexactComplex N)))]
 [tanh (from-cases ; same as sinh
        (unop -Zero) ; only exact case
-       ((Un -NonNegRat -NonNegFlonum) . -> . -NonNegFlonum) ; possible underflow, no pos -> pos
-       ((Un -NonPosRat -NonPosFlonum) . -> . -NonPosFlonum)
+       ;; possible underflow, no pos -> pos. 0 -> 0, no -NonNegRat -> -NonNegFlonum
+       ((Un -PosRat -NonNegFlonum) . -> . -NonNegFlonum)
+       ((Un -NegRat -NonPosFlonum) . -> . -NonPosFlonum)
        (map unop (list -FlonumNan -Flonum
                        -SingleFlonumNan -NonNegSingleFlonum -NonPosSingleFlonum -SingleFlonum
                        -NonNegInexactReal -NonPosInexactReal -InexactReal