diff --git a/src/framework/MOM_string_functions.F90 b/src/framework/MOM_string_functions.F90
index ddc1b41290..5c04a77b7d 100644
--- a/src/framework/MOM_string_functions.F90
+++ b/src/framework/MOM_string_functions.F90
@@ -17,7 +17,6 @@ module MOM_string_functions
 public extract_real
 public remove_spaces
 public slasher
-public append_substring
 
 contains
 
@@ -419,34 +418,6 @@ function slasher(dir)
   endif
 end function slasher
 
-!> append a string (substring) to another string (string_in) and return the
-!! concatenated string (string_out)
-function append_substring(string_in, substring) result(string_out)
-   character(len=*), intent(in) :: string_in !< input string
-   character(len=*), intent(in) :: substring !< string to append string_in
-   ! local
-   character(len=1024) :: string_out
-   character(len=1024) :: string_joined
-   integer :: string_in_length
-   integer :: substring_length
-
-   string_out = ''
-   string_joined = ''
-   string_in_length = 0
-   substring_length = 0
-
-   string_in_length = len_trim(string_in)
-   substring_length = len_trim(substring)
-
-   if (string_in_length > 0) then
-     if (substring_length > 0) then
-         string_joined = trim(string_in)//trim(substring)
-         string_out(1:len_trim(string_joined)) = trim(string_joined)
-     endif
-   endif
-
-end function append_substring
-
 !> \namespace mom_string_functions
 !!
 !!  By Alistair Adcroft and Robert Hallberg, last updated Sept. 2013.