1 files changed, 3 insertions, 1 deletions
diff --git a/math.c b/math.c
index a781167d5e..eefcec3c93 100644
--- a/math.c
+++ b/math.c
@@ -283,7 +283,9 @@ math_sinh(VALUE obj, VALUE x)
 double
 tanh(double x)
 {
-    return sinh(x) / cosh(x);
+    const double c = cosh(x);
+    if (!isinf(c)) return sinh(x) / c;
+    return x > 0 ? 1.0 : -1.0;
 }
 #endif