diff --git a/demos/fortran/submodules/container.f90 b/demos/fortran/submodules/container.f90
index 1d9387c0..d8a6c471 100644
--- a/demos/fortran/submodules/container.f90
+++ b/demos/fortran/submodules/container.f90
@@ -3,6 +3,20 @@ submodule (parent) container
 
 contains
 
+    module procedure init
+      p%mother = mother
+      p%father = father
+    end procedure init
+
+    module subroutine harmonize(p)
+      type(parent_type), intent(inout) :: p
+      real :: avg
+
+      avg = 0.5 * (p%father + p%mother)
+      p%father = avg
+      p%mother = avg
+    end subroutine harmonize
+
     module function parent_weight(p) result(w)
       type(parent_type), intent(in) :: p
       real :: w
diff --git a/demos/fortran/submodules/parent.f90 b/demos/fortran/submodules/parent.f90
index e40fbca9..17b8370b 100644
--- a/demos/fortran/submodules/parent.f90
+++ b/demos/fortran/submodules/parent.f90
@@ -7,6 +7,15 @@ module parent
   end type parent_type
 
   interface
+    module subroutine init(p, mother, father)
+      type(parent_type), intent(out) :: p
+      real, intent(in) :: mother, father
+    end subroutine init
+
+    module subroutine harmonize(p)
+      type(parent_type), intent(inout) :: p
+    end subroutine harmonize
+
     module function parent_weight(p) result(w)
       type(parent_type), intent(in) :: p
       real :: w
diff --git a/demos/fortran/submodules/submain.f90 b/demos/fortran/submodules/submain.f90
new file mode 100644
index 00000000..e47013a5
--- /dev/null
+++ b/demos/fortran/submodules/submain.f90
@@ -0,0 +1,18 @@
+program submain
+  use parent
+
+  implicit none
+
+  type(parent_type) :: a,b
+  real :: dist, weight
+
+  call init(a, 1.0, 2.0)
+  call init(b, 10.0, 12.0)
+
+  call harmonize(a)
+  weight = parent_weight(b)
+  write(*,*) weight
+  dist = parent_distance(a, b)
+  write(*,*) dist
+
+end program submain
diff --git a/demos/fortran/submodules/wscript b/demos/fortran/submodules/wscript
index 73f8be13..771614e1 100644
--- a/demos/fortran/submodules/wscript
+++ b/demos/fortran/submodules/wscript
@@ -18,3 +18,9 @@ def build(bld):
 		source = 'parent.f90 container.f90 helper.f90',
 		target = 'fudge',
 	)
+	bld(
+		features = 'fc fcprogram',
+		source = 'submain.f90',
+		use = 'fudge',
+		target = 'submain',
+	)