diff --git a/pytext/torchscript/module.py b/pytext/torchscript/module.py
index a431c8d21..bcc98a067 100644
--- a/pytext/torchscript/module.py
+++ b/pytext/torchscript/module.py
@@ -150,6 +150,8 @@ def inference_interface(self, argument_type: str):
         # LANGUAGES = 3
         # DENSE_FEAT = 4
 
+        if (sel.argno != -1):
+            raise RuntimeError("Cannot change argument type.")
         if argument_type == "texts":
             self.argno = TEXTS
         else: