Warning: The structure contains misaligned fields

Is anybody can tell me what is wrong with this? Is this a fatal error
in fortran?
Thanks!
-------------------------------
module test
implicit none

type :: ccc
sequence
private
logical :: is_null=.true.
real(8):: A0=0d0,B0=0d0, Lambda0=0d0, H0=0d0
end type ccc
end module test
-------------------------------
The compile says:

Warning: The structure contains one or more misaligned fields.
[CCC]

.

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