diff --git a/src/qmckl_ao.org b/src/qmckl_ao.org
index 40e2823..6659eef 100644
--- a/src/qmckl_ao.org
+++ b/src/qmckl_ao.org
@@ -320,7 +320,7 @@ integer function qmckl_ao_polynomial_vgl_f(context, X, R, lmax, n, L, ldl, VGL,
      return
   endif
 
-  if (lmax <= 0) then
+  if (lmax < 0) then
      info = QMCKL_INVALID_ARG_4
      return
   endif