diff --git a/ginac/inifcns_nstdsums.cpp b/ginac/inifcns_nstdsums.cpp
index a843132..a540a62 100644
--- a/ginac/inifcns_nstdsums.cpp
+++ b/ginac/inifcns_nstdsums.cpp
@@ -4066,7 +4066,12 @@ static ex zeta2_evalf(const ex& x, const ex& s)
 		return numeric(zeta_do_Hoelder_convolution(xi, si));
 	}
 
-	return zeta(x, s).hold();
+	// x and s are not lists: convert to lists
+	lst new_x_lst;
+	lst new_s_lst;
+	new_x_lst.append(x);
+	new_s_lst.append(s);
+	return zeta(new_x_lst, new_s_lst).evalf();
 }