diff --git a/tiny_gltf_loader.h b/tiny_gltf_loader.h
index 7067cdf..4b3d267 100644
--- a/tiny_gltf_loader.h
+++ b/tiny_gltf_loader.h
@@ -125,7 +125,12 @@ namespace tinygltf {
 #define TINYGLTF_IMAGE_FORMAT_BMP (2)
 #define TINYGLTF_IMAGE_FORMAT_GIF (3)
 
+#define TINYGLTF_TEXTURE_FORMAT_ALPHA (6406)
+#define TINYGLTF_TEXTURE_FORMAT_RGB (6407)
 #define TINYGLTF_TEXTURE_FORMAT_RGBA (6408)
+#define TINYGLTF_TEXTURE_FORMAT_LUMINANCE (6409)
+#define TINYGLTF_TEXTURE_FORMAT_LUMINANCE_ALPHA (6410)
+
 #define TINYGLTF_TEXTURE_TARGET_TEXTURE2D (3553)
 #define TINYGLTF_TEXTURE_TYPE_UNSIGNED_BYTE (5121)