diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2285b48..618adf2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ CMAKE_MINIMUM_REQUIRED(VERSION 3.15)
 SET(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 SET(CMAKE_C_STANDARD 99)
-# SET(CMAKE_C_EXTENSIONS OFF) # actually use c99, *not* gnu99
+SET(CMAKE_C_EXTENSIONS OFF) # actually use c99, *not* gnu99
 
 IF(CMAKE_C_COMPILER_ID MATCHES "Clang" OR CMAKE_COMPILER_ID MATCHES "GNU")
   IF(UNIX AND CMAKE_GENERATOR STREQUAL "Ninja")
@@ -106,6 +106,7 @@ IF(MAIKO_DISPLAY_SDL)
     src/sdl.c
   )
   SET(MAIKO_DISPLAY_SDL_HDRS
+    inc/sdldefs.h
   )
 ENDIF()