diff --git a/doc/source/fmpcb.rst b/doc/source/fmpcb.rst
index 87c2297e..a3dd614a 100644
--- a/doc/source/fmpcb.rst
+++ b/doc/source/fmpcb.rst
@@ -432,7 +432,7 @@ Special functions
 
     Sets *z* to the value of the Riemann zeta function `\zeta(s)`.
 
-.. function:: void fmpcb_hurwitz_zeta(fmpcb_t z, const fmpcb_t s, long prec)
+.. function:: void fmpcb_hurwitz_zeta(fmpcb_t z, const fmpcb_t s, const fmpcb_t a, long prec)
 
     Sets *z* to the value of the Hurwitz zeta function `\zeta(s, a)`.
     Note: for computing derivatives with respect to `s`, see the