submodules

There is a compilation issue occured when circular reference is employed. See the codes:

module test1
    implicit none

    integer, parameter :: a = 5

    interface
        module subroutine sub1()
        end subroutine sub1
    end interface

end module test1

submodule(test1) submodule1
    use test2
    implicit none

    contains

    module procedure sub1
        implicit none
        print*, b
    end procedure sub1

end submodule submodule1

module test2
    implicit none

    integer, parameter :: b = 4

    interface
        module subroutine sub2()
        end subroutine sub2
    end interface

end module test2

submodule(test2) submodule2
    use test1
    implicit none

    contains

    module procedure sub2
        implicit none
        print*, a
    end procedure sub2

end submodule submodule2

program main
    use test1
    use test2

    !TO DO.

end program main

The use association in submodules are permitted by the standard. An error shows up when compile for the first time:

error #7002: Error in opening the compiled module file.  Check INCLUDE paths.   [TEST2]

If then we compile it again without cleanning-up, the target assembly will be created successfully. So is it a compiler mistake ? Or how should I do to solve it ?