diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a9b76f..f6ca5b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -31,6 +31,7 @@ set(WITH_TESTSUITE OFF CACHE BOOL "" FORCE)
 set(WITH_MAIN ON CACHE BOOL "" FORCE)
 add_subdirectory(third-party/corrade EXCLUDE_FROM_ALL)
 
+set(DIRECTX OFF CACHE BOOL "" FORCE) # We use OpenGL.
 set(SDL_ATOMIC OFF CACHE BOOL "" FORCE)
 set(SDL_CPUINFO OFF CACHE BOOL "" FORCE)
 set(SDL_EVENTS ON CACHE BOOL "" FORCE)