1 files changed, 1 insertions, 1 deletions
diff --git a/math.c b/math.c
index ba5a12128a..d4a24d2b45 100644
--- a/math.c
+++ b/math.c
@@ -122,7 +122,7 @@ math_sinh(obj, x)
     return rb_float_new(sinh(RFLOAT(x)->value));
 }
 
-#ifndef HAVE_SINH
+#ifndef HAVE_TANH
 double
 tanh(x)
     double x;