diff --git a/cmake/modules/ListToString.cmake b/cmake/modules/ListToString.cmake
index 8063e15..ec705fa 100644
--- a/cmake/modules/ListToString.cmake
+++ b/cmake/modules/ListToString.cmake
@@ -1,29 +1,30 @@
-if(NOT DEFINED LIST_TO_STRING_LOADED)
-
-    function(list_to_string separator prefix suffix input_list output_string_var)
-        set(res "")
-        # get list length
-        list(LENGTH input_list list_length)
-        # if the list has 0 or 1 element, there is no need to loop over
-        if(list_length LESS 2)
-            set(res "${prefix}${input_list}${suffix}")
-        else()
-            math(EXPR last_element_index "${list_length} - 1")
-            foreach(index RANGE ${last_element_index})
-                # get current item_value
-                list(GET input_list ${index} item_value)
-                if(NOT item_value STREQUAL "")
-                    # .. and append non-empty value to output string
-                    set(res "${res}${prefix}${item_value}${suffix}")
-                    # append separator if current element is NOT the last one.
-                    if(NOT index EQUAL last_element_index)
-                        set(res "${res}${separator}")
-                    endif()
-                endif()
-            endforeach()
-        endif()
-        set(${output_string_var} "${res}" PARENT_SCOPE)
-    endfunction()
-
-    set(LIST_TO_STRING_LOADED YES)
+# prevent multiple inclusion
+if(DEFINED LIST_TO_STRING_LOADED)
+    return()
 endif()
+set(LIST_TO_STRING_LOADED ON)
+
+function(list_to_string separator prefix suffix input_list output_string_var)
+    set(res "")
+    # get list length
+    list(LENGTH input_list list_length)
+    # if the list has 0 or 1 element, there is no need to loop over
+    if(list_length LESS 2)
+        set(res "${prefix}${input_list}${suffix}")
+    else()
+        math(EXPR last_element_index "${list_length} - 1")
+        foreach(index RANGE ${last_element_index})
+            # get current item_value
+            list(GET input_list ${index} item_value)
+            if(NOT item_value STREQUAL "")
+                # .. and append non-empty value to output string
+                set(res "${res}${prefix}${item_value}${suffix}")
+                # append separator if current element is NOT the last one.
+                if(NOT index EQUAL last_element_index)
+                    set(res "${res}${separator}")
+                endif()
+            endif()
+        endforeach()
+    endif()
+    set(${output_string_var} "${res}" PARENT_SCOPE)
+endfunction()