Fixed the name of the environment variable to match the name of the hint.
diff --git a/include/SDL_hints.h b/include/SDL_hints.h
index e90ba2e..9dc9cfe 100644
--- a/include/SDL_hints.h
+++ b/include/SDL_hints.h
@@ -260,7 +260,7 @@ extern "C" {
/**
* \brief If set to 1, then do not allow high-DPI windows. ("Retina" on Mac)
*/
-#define SDL_HINT_VIDEO_HIGHDPI_DISABLED "SDL_HIGHDPI_DISABLED"
+#define SDL_HINT_VIDEO_HIGHDPI_DISABLED "SDL_VIDEO_HIGHDPI_DISABLED"
/**