diff --git a/io_scene_obj/__init__.py b/io_scene_obj/__init__.py
index 4fc670a9a99f5c03439ece47df42a998f43fd233..ac396b7ea7c188cc2b1131441548701fc2dcc140 100644
--- a/io_scene_obj/__init__.py
+++ b/io_scene_obj/__init__.py
@@ -21,7 +21,7 @@
 bl_info = {
     "name": "Wavefront OBJ format",
     "author": "Campbell Barton, Bastien Montagne",
-    "version": (3, 4, 0),
+    "version": (3, 4, 1),
     "blender": (2, 80, 0),
     "location": "File > Import-Export",
     "description": "Import-Export OBJ, Import OBJ mesh, UV's, materials and textures",
diff --git a/io_scene_obj/import_obj.py b/io_scene_obj/import_obj.py
index 8f914d6e237d699aedfca7c6902c93b206d56096..55e7648c9a01e5a386ed3b0b3e2a8c0b24b29e7c 100644
--- a/io_scene_obj/import_obj.py
+++ b/io_scene_obj/import_obj.py
@@ -148,7 +148,7 @@ def create_materials(filepath, relpath,
 
         elif type == 'Bump':
             bump_mult = map_options.get(b'-bm')
-            bump_mult = float(bump_mult[0]) if (bump_mult is not None and len(bump_mult) > 1) else 1.0
+            bump_mult = float(bump_mult[0]) if (bump_mult and len(bump_mult[0]) > 1) else 1.0
             mat_wrap.normalmap_strength_set(bump_mult)
 
             _generic_tex_set(mat_wrap.normalmap_texture, image, 'UV', map_offset, map_scale)