diff --git a/io_scene_fbx/__init__.py b/io_scene_fbx/__init__.py
index bb0f8ae1d5566228ea4223da9a87e5c96bce7950..893c13d2e049a5c806dda34a839b135bf9586c4e 100644
--- a/io_scene_fbx/__init__.py
+++ b/io_scene_fbx/__init__.py
@@ -21,7 +21,7 @@
 bl_info = {
     "name": "FBX format",
     "author": "Campbell Barton, Bastien Montagne, Jens Restemeier",
-    "version": (4, 20, 0),
+    "version": (4, 20, 1),
     "blender": (2, 81, 6),
     "location": "File > Import-Export",
     "description": "FBX IO meshes, UV's, vertex colors, materials, textures, cameras, lamps and actions",
diff --git a/io_scene_fbx/fbx_utils.py b/io_scene_fbx/fbx_utils.py
index f71e89a8153171e642a9959c16d7be972bc57756..c35399b24cd8ff021e8379a5ad80ff71ff21996d 100644
--- a/io_scene_fbx/fbx_utils.py
+++ b/io_scene_fbx/fbx_utils.py
@@ -594,10 +594,12 @@ def _elem_props_flags(animatable, animated, custom):
                 return b"A+U"
             return b"A+"
         if custom:
-            return b"AU"
+            # Seems that customprops always need those 'flags', see T69554. Go figure...
+            return b"A+U"
         return b"A"
     if custom:
-        return b"U"
+        # Seems that customprops always need those 'flags', see T69554. Go figure...
+        return b"A+U"
     return b""