diff --git a/lib/vagrant-libvirt/action/handle_box_image.rb b/lib/vagrant-libvirt/action/handle_box_image.rb
index 2b621d7..45b7691 100644
--- a/lib/vagrant-libvirt/action/handle_box_image.rb
+++ b/lib/vagrant-libvirt/action/handle_box_image.rb
@@ -96,7 +96,14 @@ module VagrantPlugins
             volume = pool.lookup_volume_by_name(volume_name)
             stream = env[:libvirt_compute].client.stream
             volume.upload(stream, offset=0, length=image_size)
-            buf_size = 1024*1024 # 1M
+
+            # Exception Libvirt::RetrieveError can be raised if buffer is
+            # longer than length accepted by API send function.
+            # 
+            # TODO: How to find out if buffer is too large and what is the
+            # length that send function will accept?
+
+            buf_size = 1024*250 # 250K
             progress = 0
             open(image_file, 'rb') do |io|
               while (buff = io.read(buf_size)) do
diff --git a/lib/vagrant-libvirt/errors.rb b/lib/vagrant-libvirt/errors.rb
index 1aafa85..322bf6a 100644
--- a/lib/vagrant-libvirt/errors.rb
+++ b/lib/vagrant-libvirt/errors.rb
@@ -25,7 +25,7 @@ module VagrantPlugins
       end
 
       class ImageUploadError < VagrantLibvirtError
-        error_key(:image_upload_error_error)
+        error_key(:image_upload_error)
       end