diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6dd5d9d172..50d7fbaf37 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -299,7 +299,6 @@ if(IPO_FOUND)
     set_target_properties(openttd PROPERTIES INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO True)
 endif()
 set_target_properties(openttd PROPERTIES VS_DEBUGGER_WORKING_DIRECTORY "${CMAKE_BINARY_DIR}")
-process_compile_flags()
 
 include(LinkPackage)
 link_package(PNG TARGET PNG::PNG ENCOURAGED)
diff --git a/cmake/SourceList.cmake b/cmake/SourceList.cmake
index f01f5db86b..6c9ebe933f 100644
--- a/cmake/SourceList.cmake
+++ b/cmake/SourceList.cmake
@@ -46,44 +46,3 @@ endfunction()
 function(add_test_files)
     _add_files_tgt(openttd_test ${ARGV})
 endfunction()
-
-# This function works around an 'issue' with CMake, where
-# set_source_files_properties() only works in the scope of the file. We want
-# to set properties for the source file on a more global level. To solve this,
-# this function records the flags you want, and a macro adds them in the root
-# CMakeLists.txt.
-# See this URL for more information on the issue:
-# http://cmake.3232098.n2.nabble.com/scope-of-set-source-files-properties-td4766111.html
-#
-# set_compile_flags([file1 ...] COMPILE_FLAGS cflag [cflag ...])
-#
-function(set_compile_flags)
-    cmake_parse_arguments(PARAM "" "" "COMPILE_FLAGS" ${ARGN})
-    set(PARAM_FILES "${PARAM_UNPARSED_ARGUMENTS}")
-
-    get_property(SOURCE_PROPERTIES GLOBAL PROPERTY source_properties)
-
-    foreach(FILE IN LISTS PARAM_FILES)
-        list(APPEND SOURCE_PROPERTIES "${CMAKE_CURRENT_SOURCE_DIR}/${FILE}::${PARAM_COMPILE_FLAGS}")
-    endforeach()
-
-    set_property(GLOBAL PROPERTY source_properties "${SOURCE_PROPERTIES}")
-endfunction()
-
-# Call this macro in the same CMakeLists.txt and after add_executable().
-# This makes sure all the COMPILE_FLAGS of set_compile_flags() are set
-# correctly.
-#
-# process_compile_flags()
-#
-function(process_compile_flags)
-    get_property(SOURCE_PROPERTIES GLOBAL PROPERTY source_properties)
-
-    foreach(ENTRY ${SOURCE_PROPERTIES})
-        string(REPLACE "::" ";" ENTRY "${ENTRY}")
-        list(GET ENTRY 0 FILE)
-        list(GET ENTRY 1 PROPERTIES)
-
-        set_source_files_properties(${FILE} PROPERTIES COMPILE_FLAGS ${PROPERTIES})
-    endforeach()
-endfunction()