diff --git a/io_export_psk_psa/psa/operator.py b/io_export_psk_psa/psa/operator.py
index 227e7a1..019b6d8 100644
--- a/io_export_psk_psa/psa/operator.py
+++ b/io_export_psk_psa/psa/operator.py
@@ -56,8 +56,9 @@ class PsaExportOperator(Operator, ExportHelper):
         row.template_list('PSA_UL_ActionList', 'asd', scene, 'psa_action_list', scene, 'psa_action_list_index', rows=len(context.scene.psa_action_list))
 
     def is_action_for_armature(self, action):
+        if len(action.fcurves) == 0:
+            return False
         bone_names = [x.name for x in self.armature.data.bones]
-        print(bone_names)
         for fcurve in action.fcurves:
             match = re.match('pose\.bones\["(.+)"\].\w+', fcurve.data_path)
             if not match:
diff --git a/io_export_psk_psa/psk/builder.py b/io_export_psk_psa/psk/builder.py
index 2078fc2..a5d9698 100644
--- a/io_export_psk_psa/psk/builder.py
+++ b/io_export_psk_psa/psk/builder.py
@@ -26,6 +26,9 @@ class PskBuilder(object):
         armature_modifier = modifiers[0]
         armature_object = armature_modifier.object
 
+        if object.modifiers[-1] != armature_modifier:
+            raise RuntimeError('Armature modifier must be the last modifier in the stack')
+
         if armature_object is None:
             raise RuntimeError('Armature modifier has no linked object')
 
@@ -97,6 +100,7 @@ class PskBuilder(object):
                 psk.wedges[f.loops[i]].material_index = f.material_index
 
         # https://github.com/bwrsandman/blender-addons/blob/master/io_export_unreal_psk_psa.py
+        # TODO: maybe we should use the EDIT bones instead???
         bones = list(armature_object.data.bones)
         for bone in bones:
             psk_bone = Psk.Bone()
diff --git a/io_export_psk_psa/psk/operator.py b/io_export_psk_psa/psk/operator.py
index c51d0f4..9505eb8 100644
--- a/io_export_psk_psa/psk/operator.py
+++ b/io_export_psk_psa/psk/operator.py
@@ -18,6 +18,38 @@ class PskExportOperator(Operator, ExportHelper):
         maxlen=1024,
         default='')
 
+    def invoke(self, context, event):
+        object = context.view_layer.objects.active
+
+        if object.type != 'MESH':
+            self.report({'ERROR_INVALID_CONTEXT'}, 'The selected object must be a mesh.')
+            return {'CANCELLED'}
+
+        if len(object.data.materials) == 0:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'Mesh must have at least one material')
+            return {'CANCELLED'}
+
+        # ensure that there is exactly one armature modifier
+        modifiers = [x for x in object.modifiers if x.type == 'ARMATURE']
+
+        if len(modifiers) != 1:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'Mesh must have one armature modifier')
+            return {'CANCELLED'}
+
+        armature_modifier = modifiers[0]
+        armature_object = armature_modifier.object
+
+        if object.modifiers[-1] != armature_modifier:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'Armature modifier must be the last modifier in the stack')
+            return {'CANCELLED'}
+
+        if armature_object is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'Armature modifier has no linked object')
+            return {'CANCELLED'}
+
+        context.window_manager.fileselect_add(self)
+        return {'RUNNING_MODAL'}
+
     def execute(self, context):
         builder = PskBuilder()
         psk = builder.build(context)