The attached patch has been tested on x86_64-*-freebsd. I plan to commit this patch tomorrow if there are no objections. A BOZ literal constant cannot appear in an output IO list. By default, the patch will generate an error. The -fallow-invalid-boz option can be used to degrade the error into an warning. The resulting executable then has historic broken gfortran behavior. 2019-09-03 Steven G. Kargl PR fortran/91650 * io.c (match_io_element): An output IO list item cannot be a BOZ. 2019-09-03 Steven G. Kargl PR fortran/91650 * gfortran.dg/pr91650_1.f90: New test. * gfortran.dg/pr91650_2.f90: Ditto. -- Steve