diff --git a/trimesh/exchange/gltf.py b/trimesh/exchange/gltf.py
index <HASH>..<HASH> 100644
--- a/trimesh/exchange/gltf.py
+++ b/trimesh/exchange/gltf.py
@@ -1122,6 +1122,10 @@ def _append_material(mat, tree, buffer_items):
     except BaseException:
         pass
 
+    # if alphaMode is defined, export
+    if isinstance(mat.alphaMode, str):
+        pbr['alphaMode'] = mat.alphaMode
+
     # if scalars are defined correctly export
     if isinstance(mat.metallicFactor, float):
         pbr['metallicFactor'] = mat.metallicFactor
diff --git a/trimesh/visual/material.py b/trimesh/visual/material.py
index <HASH>..<HASH> 100644
--- a/trimesh/visual/material.py
+++ b/trimesh/visual/material.py
@@ -135,7 +135,7 @@ class PBRMaterial(Material):
         self.doubleSided = doubleSided
 
         # str
-        alphaMode = alphaMode
+        self.alphaMode = alphaMode
 
     def to_color(self, uv):
         """
Preserves the alphaMode when reading and writing gltf