diff --git a/app/models/media_attachment.rb b/app/models/media_attachment.rb
index d913e7372a7..e4a974f9683 100644
--- a/app/models/media_attachment.rb
+++ b/app/models/media_attachment.rb
@@ -25,6 +25,9 @@ class MediaAttachment < ApplicationRecord
 
   enum type: [:image, :gifv, :video, :unknown]
 
+  IMAGE_FILE_EXTENSIONS = ['.jpg', '.jpeg', '.png', '.gif'].freeze
+  VIDEO_FILE_EXTENSIONS = ['.webm', '.mp4', '.m4v'].freeze
+
   IMAGE_MIME_TYPES = ['image/jpeg', 'image/png', 'image/gif'].freeze
   VIDEO_MIME_TYPES = ['video/webm', 'video/mp4'].freeze
 
diff --git a/app/serializers/initial_state_serializer.rb b/app/serializers/initial_state_serializer.rb
index 9ee9bd29c82..88bbc0dff3c 100644
--- a/app/serializers/initial_state_serializer.rb
+++ b/app/serializers/initial_state_serializer.rb
@@ -46,6 +46,6 @@ class InitialStateSerializer < ActiveModel::Serializer
   end
 
   def media_attachments
-    { accept_content_types: MediaAttachment::IMAGE_MIME_TYPES + MediaAttachment::VIDEO_MIME_TYPES }
+    { accept_content_types: MediaAttachment::IMAGE_FILE_EXTENSIONS + MediaAttachment::VIDEO_FILE_EXTENSIONS + MediaAttachment::IMAGE_MIME_TYPES + MediaAttachment::VIDEO_MIME_TYPES }
   end
 end