diff --git a/src/post_modules/Nettle/hogweed.cmod b/src/post_modules/Nettle/hogweed.cmod
index ad5d5ffd7fb5b7b4afa5bdcd9731912d8d30235e..46014e81b7b80b43979d13b6cecf2c0d96535d5e 100644
--- a/src/post_modules/Nettle/hogweed.cmod
+++ b/src/post_modules/Nettle/hogweed.cmod
@@ -492,6 +492,9 @@ PIKECLASS ECC_Curve
    *!
    *! @returns
    *!   Returns the new point on the curve.
+   *!
+   *! @throws
+   *!   Throws an error if the point (@[x], @[y]) isn't on the curve.
    */
   PIKEFUN array(object(Gmp.mpz)) point_mul(object(Gmp.mpz)|int x,
 					   object(Gmp.mpz)|int y,