diff --git a/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py b/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
index 486aeea66..189914370 100644
--- a/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
+++ b/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
@@ -208,7 +208,7 @@ def __encode_from_image(self, image: bpy.types.Image) -> bytes:
                     with open(src_path, 'rb') as f:
                         data = f.read()
         # Check magic number is right
-        if data and self.check_magic(data):
+        if data and self.__check_magic(data):
             return data
 
         # Copy to a temp image and save.