diff --git a/src/assert_m.F90 b/src/assert/assert_subroutine_m.F90
similarity index 97%
rename from src/assert_m.F90
rename to src/assert/assert_subroutine_m.F90
index 9ca765d..90e0e11 100644
--- a/src/assert_m.F90
+++ b/src/assert/assert_subroutine_m.F90
@@ -4,7 +4,7 @@
 !     "Multi-Dimensional Physics Implementation into Fuel Analysis under Steady-state and Transients (FAST)",
 !     contract # NRC-HQ-60-17-C-0007
 !
-module assert_m
+module assert_subroutine_m
   !! summary: Utility for runtime checking of logical assertions.
   !! usage: error-terminate if the assertion fails:
   !!
@@ -44,4 +44,4 @@ pure module subroutine assert(assertion, description, diagnostic_data)
 
   end interface
 
-end module
+end module assert_subroutine_m
diff --git a/src/assert_s.f90 b/src/assert/assert_subroutine_s.f90
similarity index 96%
rename from src/assert_s.f90
rename to src/assert/assert_subroutine_s.f90
index 5cdda34..5e95e27 100644
--- a/src/assert_s.f90
+++ b/src/assert/assert_subroutine_s.f90
@@ -4,7 +4,7 @@
 !     "Multi-Dimensional Physics Implementation into Fuel Analysis under Steady-state and Transients (FAST)",
 !     contract # NRC-HQ-60-17-C-0007
 !
-submodule(assert_m) assert_s
+submodule(assert_subroutine_m) assert_subroutine_s
   implicit none
 
 contains
@@ -84,4 +84,4 @@ end function string
 
   end procedure
 
-end submodule
+end submodule assert_subroutine_s
diff --git a/src/characterizable_m.f90 b/src/assert/characterizable_m.f90
similarity index 100%
rename from src/characterizable_m.f90
rename to src/assert/characterizable_m.f90
diff --git a/src/intrinsic_array_m.F90 b/src/assert/intrinsic_array_m.f90
similarity index 96%
rename from src/intrinsic_array_m.F90
rename to src/assert/intrinsic_array_m.f90
index 2be48c8..53c9716 100644
--- a/src/intrinsic_array_m.F90
+++ b/src/assert/intrinsic_array_m.f90
@@ -35,11 +35,7 @@ module intrinsic_array_m
     
     pure module function construct(array) result(intrinsic_array)
       implicit none
-#ifndef NAGFOR
       class(*), intent(in) :: array(..)
-#else
-      class(*), intent(in) :: array(:)
-#endif
       type(intrinsic_array_t) intrinsic_array
     end function
     
diff --git a/src/intrinsic_array_s.F90 b/src/assert/intrinsic_array_s.f90
similarity index 99%
rename from src/intrinsic_array_s.F90
rename to src/assert/intrinsic_array_s.f90
index 2db2c86..9ea16e3 100644
--- a/src/intrinsic_array_s.F90
+++ b/src/assert/intrinsic_array_s.f90
@@ -5,10 +5,8 @@
 
   module procedure construct
 
-#ifndef NAGFOR
   select rank(array)
     rank(1)
-#endif
       select type(array)
       type is(complex)
         allocate(intrinsic_array%complex_1D, source = array)
@@ -23,7 +21,6 @@
       class default
         error  stop "intrinsic_array_t construct: unsupported rank-2 type"
       end select
-#ifndef NAGFOR
     rank(2)
       select type(array)
       type is(complex)
@@ -59,7 +56,6 @@
     rank default
       error  stop "intrinsic_array_t construct: unsupported rank"
     end select
-#endif
 
   end procedure
 
diff --git a/src/assert_m.f90 b/src/assert_m.f90
new file mode 100644
index 0000000..23f36c5
--- /dev/null
+++ b/src/assert_m.f90
@@ -0,0 +1,6 @@
+module assert_m
+  use intrinsic_array_m
+  use assert_subroutine_m
+  use characterizable_m
+  implicit none
+end module assert_m