diff --git a/src/assert/assert_subroutine_m.F90 b/src/assert/assert_subroutine_m.F90
index cdaadfe..8fd0a68 100644
--- a/src/assert/assert_subroutine_m.F90
+++ b/src/assert/assert_subroutine_m.F90
@@ -7,6 +7,8 @@
 !
 #include "assert_macros.h"
 
+#include "assert_features.h"
+
 module assert_subroutine_m
   !! summary: Utility for runtime enforcement of logical assertions.
   !! usage: error-terminate if the assertion fails:
@@ -66,9 +68,10 @@ pure subroutine assert_error_stop_interface(stop_code_char)
 #endif
   logical, parameter :: enforce_assertions=USE_ASSERTIONS
 
-  interface
 
-    pure module subroutine assert(assertion, description)
+contains
+
+    pure subroutine assert(assertion, description)
       !! If assertion is .false. and enforcement is enabled (e.g. via -DASSERTIONS=1),
       !! then error-terminate with a character stop code that contains the description argument if present
       implicit none
@@ -76,15 +79,50 @@ pure module subroutine assert(assertion, description)
         !! Most assertions will be expressions such as i>0
       character(len=*), intent(in) :: description
         !! A brief statement of what is being asserted such as "i>0" or "positive i"
-    end subroutine
 
-    pure module subroutine assert_always(assertion, description)
+    toggle_assertions: &
+    if (enforce_assertions) then
+        call assert_always(assertion, description)
+    end if toggle_assertions
+    
+  end subroutine
+
+    pure subroutine assert_always(assertion, description)
       !! Same as above but always enforces the assertion (regardless of ASSERTIONS)
       implicit none
       logical, intent(in) :: assertion
       character(len=*), intent(in) :: description
-    end subroutine
+    character(len=:), allocatable :: message
+    integer me
 
-  end interface
+      check_assertion: &
+      if (.not. assertion) then
+
+#if ASSERT_MULTI_IMAGE
+#  if ASSERT_PARALLEL_CALLBACKS
+        me = assert_this_image()
+#  else
+        me = this_image()
+#  endif
+   block
+        character(len=128) image_number
+        write(image_number, *) me
+        message = 'Assertion failure on image ' // trim(adjustl(image_number)) // ':' // description 
+   end block
+#else
+        message = 'Assertion failure: ' // description
+        me = 0 ! avoid a harmless warning
+#endif
+ 
+#if ASSERT_PARALLEL_CALLBACKS
+        call assert_error_stop(message)
+#else
+        error stop message, QUIET=.false.
+#endif
+
+      end if check_assertion
+
+  end subroutine
 
 end module assert_subroutine_m
+
diff --git a/src/assert/assert_subroutine_s.F90 b/src/assert/assert_subroutine_s.F90
deleted file mode 100644
index d73901f..0000000
--- a/src/assert/assert_subroutine_s.F90
+++ /dev/null
@@ -1,79 +0,0 @@
-!
-!     (c) 2019-2020 Guide Star Engineering, LLC
-!     This Software was developed for the US Nuclear Regulatory Commission (US NRC) under contract
-!     "Multi-Dimensional Physics Implementation into Fuel Analysis under Steady-state and Transients (FAST)",
-!     contract # NRC-HQ-60-17-C-0007
-!
-
-#include "assert_features.h"
-
-submodule(assert_subroutine_m) assert_subroutine_s
-  implicit none
-
-contains
-
-  module procedure assert
-
-    toggle_assertions: &
-    if (enforce_assertions) then
-        call assert_always(assertion, description)
-    end if toggle_assertions
-    
-  end procedure
-
-  module procedure assert_always
-    character(len=:), allocatable :: message
-    integer me
-
-      check_assertion: &
-      if (.not. assertion) then
-
-#if ASSERT_MULTI_IMAGE
-#  if ASSERT_PARALLEL_CALLBACKS
-        me = assert_this_image()
-#  else
-        me = this_image()
-#  endif
-        message = 'Assertion failure on image ' // string(me) // ':' // description 
-#else
-        message = 'Assertion failure: ' // description
-        me = 0 ! avoid a harmless warning
-#endif
- 
-#if ASSERT_PARALLEL_CALLBACKS
-        call assert_error_stop(message)
-#else
-        error stop message, QUIET=.false.
-#endif
-
-      end if check_assertion
-
-  contains
-    
-    pure function string(numeric) result(number_as_string)
-      !! Result is a string represention of the numeric argument
-      class(*), intent(in) :: numeric
-      integer, parameter :: max_len=128
-      character(len=max_len) :: untrimmed_string
-      character(len=:), allocatable :: number_as_string
-
-      select type(numeric)
-        type is(complex)
-          write(untrimmed_string, *) numeric
-        type is(integer)
-          write(untrimmed_string, *) numeric
-        type is(logical)
-          write(untrimmed_string, *) numeric
-        type is(real)
-          write(untrimmed_string, *) numeric
-        class default
-          error stop "Internal error in subroutine 'assert': unsupported type in function 'string'."
-      end select
-
-      number_as_string = trim(adjustl(untrimmed_string))
-
-    end function string
-
-  end procedure
-
-end submodule assert_subroutine_s
diff --git a/test/test-assert-subroutine-error-termination.F90 b/test/test-assert-subroutine-error-termination.F90
index 07ac2d3..ea94fbd 100644
--- a/test/test-assert-subroutine-error-termination.F90
+++ b/test/test-assert-subroutine-error-termination.F90
@@ -27,7 +27,8 @@ program test_assert_subroutine_error_termination
 #elif _CRAYFTN
     command = "fpm run --example false-assertion --profile release --compiler crayftn.sh --flag '-DASSERTIONS' > /dev/null 2>&1", &
 #else
-    command = "echo 'example/false_assertion.F90: unsupported compiler' && exit 1", &
+    ! For all other compilers, we assume that the default fpm command works
+    command = "fpm run --example false-assertion --profile release --flag '-DASSERTIONS -ffree-line-length-0' > /dev/null 2>&1", &
 #endif
     wait = .true., &
     exitstat = exit_status &
@@ -47,15 +48,18 @@ program test_assert_subroutine_error_termination
       end if
     end if
   end block
+#else
+#ifdef __LFORTRAN__
+    print *,trim(merge("passes","FAILS ",exit_status/=0)) // " on error-terminating when assertion = .false."
 #else
     block
       integer unit
       open(newunit=unit, file="build/exit_status", status="old")
       read(unit,*) exit_status
-      print *,trim(merge("passes","FAILS ",exit_status/=0)) // " on error-terminating when assertion = .false."
       close(unit)
     end block 
 #endif
+#endif
 
 contains