diff --git a/cparser/Cutil.ml b/cparser/Cutil.ml
index 0ef96ddd1..9c11dcec5 100644
--- a/cparser/Cutil.ml
+++ b/cparser/Cutil.ml
@@ -609,6 +609,8 @@ let sizeof_layout_struct env members ma =
                          (record_field m.fld_name pos :: accu)
                          rem
           | Some width ->
+              (* bit fields must be naturally aligned *)
+              assert (alignas_attribute (attributes_of_type env m.fld_typ) = 0);
               (* curr = beginning of storage unit, in bits
                  next = one past end of storage unit, in bits *)
               let curr = pos / (a * 8) * (a * 8) in
diff --git a/cparser/Elab.ml b/cparser/Elab.ml
index 7bbb43199..dc2a3c62c 100644
--- a/cparser/Elab.ml
+++ b/cparser/Elab.ml
@@ -1086,7 +1086,7 @@ and elab_field_group env = function
             error loc
               "the type of bit-field '%a' must be an integer type no bigger than 'int'" pp_field id;
             None,env
-          end else if has_std_alignas env' ty then begin
+          end else if alignas_attribute (attributes_of_type env' ty) > 0 then begin
             error loc "alignment specified for bit-field '%a'" pp_field id;
             None, env
           end else begin