diff --git a/include/math.lusi b/include/math.lusi
index 8033408bbb2ca7a3d7878a3c8df2c22caba7f9b8..68b2d3826365e90916b5fb7852eac320f375de66 100644
--- a/include/math.lusi
+++ b/include/math.lusi
@@ -14,4 +14,5 @@ function fabs (x: real) returns (y: real) prototype C lib m;
 function pow (x:real; n: real) returns (y: real) prototype C lib m;
 function sin (x: real) returns (y: real) prototype C lib m;
 function sinh (x: real) returns (y: real) prototype C lib m;
-function sqrt (x: real) returns (y: real) prototype C lib m;
\ No newline at end of file
+function sqrt (x: real) returns (y: real) prototype C lib m;
+function tan (x: real) returns (y: real) prototype C lib m;