{tag, PB_ATYPE_CALLBACK | PB_HTYPE_REPEATED | ltype, \
fd, 0, pb_membersize(st, m), 0, ptr}
-/* Optional extensions don't have the has_ field, as that would be redundant. */
+/* Optional extensions don't have the has_ field, as that would be redundant.
+ * Furthermore, the combination of OPTIONAL without has_ field is used
+ * for indicating proto3 style fields. Extensions exist in proto2 mode only,
+ * so they should be encoded according to proto2 rules. To avoid the conflict,
+ * extensions are marked as REQUIRED instead.
+ */
#define PB_OPTEXT_STATIC(tag, st, m, fd, ltype, ptr) \
- {tag, PB_ATYPE_STATIC | PB_HTYPE_OPTIONAL | ltype, \
+ {tag, PB_ATYPE_STATIC | PB_HTYPE_REQUIRED | ltype, \
0, \
0, \
pb_membersize(st, m), 0, ptr}