diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index 4327263af..67ce6cc0d 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -537,7 +537,7 @@ elseif( APPLE )
 	set_source_files_properties( platform/posix/osx/${PROJECT_NAME}.icns PROPERTIES MACOSX_PACKAGE_LOCATION Resources )
 	set_source_files_properties( platform/posix/osx/iwadpicker_cocoa.mm PROPERTIES COMPILE_FLAGS -fobjc-exceptions )
 else()
-	set( SYSTEM_SOURCES_DIR platform/posix platform/posix/sdl )
+	set( SYSTEM_SOURCES_DIR platform/posix/sdl )
 	set( SYSTEM_SOURCES ${PLAT_POSIX_SOURCES} ${PLAT_SDL_SOURCES} ${PLAT_UNIX_SOURCES} )
 	set( OTHER_SYSTEM_SOURCES ${PLAT_WIN32_SOURCES} ${PLAT_OSX_SOURCES} ${PLAT_COCOA_SOURCES} )
 endif()