diff --git a/mhcflurry/multiallelic_refinement_command.py b/mhcflurry/multiallelic_refinement_command.py
index cc8ca67585eae88a10d93d4884675934057bc304..38cbb0e5368d7bbce82c6ebc2abe30bc8b5a4c94 100644
--- a/mhcflurry/multiallelic_refinement_command.py
+++ b/mhcflurry/multiallelic_refinement_command.py
@@ -74,7 +74,6 @@ parser.add_argument(
     default=None)
 parser.add_argument(
     "--only-alleles-with-mass-spec",
-    type=bool,
     default=False,
     action="store_true")
 parser.add_argument(