diff --git a/cmake/SourceList.cmake b/cmake/SourceList.cmake
index af87c09e82..7be406050e 100644
--- a/cmake/SourceList.cmake
+++ b/cmake/SourceList.cmake
@@ -1,12 +1,4 @@
-# Add a file to be compiled.
-#
-# add_files([file1 ...] CONDITION condition [condition ...])
-#
-# CONDITION is a complete statement that can be evaluated with if().
-# If it evaluates true, the source files will be added; otherwise not.
-# For example: ADD_IF SDL_FOUND AND Allegro_FOUND
-#
-function(add_files)
+function(_add_files_tgt tgt)
     cmake_parse_arguments(PARAM "" "" "CONDITION" ${ARGN})
     set(PARAM_FILES "${PARAM_UNPARSED_ARGUMENTS}")
 
@@ -21,6 +13,18 @@ function(add_files)
     endforeach()
 endfunction()
 
+# Add a file to be compiled.
+#
+# add_files([file1 ...] CONDITION condition [condition ...])
+#
+# CONDITION is a complete statement that can be evaluated with if().
+# If it evaluates true, the source files will be added; otherwise not.
+# For example: ADD_IF SDL_FOUND AND Allegro_FOUND
+#
+function(add_files)
+    _add_files_tgt(openttd_lib ${ARGV})
+endfunction()
+
 # Add a test file to be compiled.
 #
 # add_test_files([file1 ...] CONDITION condition [condition ...])
@@ -30,18 +34,7 @@ endfunction()
 # For example: ADD_IF SDL_FOUND AND Allegro_FOUND
 #
 function(add_test_files)
-    cmake_parse_arguments(PARAM "" "" "CONDITION" ${ARGN})
-    set(PARAM_FILES "${PARAM_UNPARSED_ARGUMENTS}")
-
-    if(PARAM_CONDITION)
-        if(NOT (${PARAM_CONDITION}))
-            return()
-        endif()
-    endif()
-
-    foreach(FILE IN LISTS PARAM_FILES)
-        target_sources(openttd_test PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/${FILE})
-    endforeach()
+    _add_files_tgt(openttd_test ${ARGV})
 endfunction()
 
 # This function works around an 'issue' with CMake, where