diff --git a/caikit_nlp/toolkit/text_generation/model_run_utils.py b/caikit_nlp/toolkit/text_generation/model_run_utils.py
index ac33130b..49cee8d7 100644
--- a/caikit_nlp/toolkit/text_generation/model_run_utils.py
+++ b/caikit_nlp/toolkit/text_generation/model_run_utils.py
@@ -167,7 +167,7 @@ def generate_text_func(
         GENERATE_FUNCTION_ARGS
     )
 
-    error.type_check("<NLP85452187E>", str, eos_token=eos_token)
+    error.type_check("<NLP85452187E>", str, allow_none=True, eos_token=eos_token)
     error.type_check("<NLP65883534E>", str, text=text)
 
     error.type_check(
diff --git a/caikit_nlp/toolkit/text_generation/tgis_utils.py b/caikit_nlp/toolkit/text_generation/tgis_utils.py
index 16bf99b9..26ede868 100644
--- a/caikit_nlp/toolkit/text_generation/tgis_utils.py
+++ b/caikit_nlp/toolkit/text_generation/tgis_utils.py
@@ -73,7 +73,7 @@ def validate_inf_params(
     )
     error.type_check("<NLP65883535E>", str, text=text)
     error.type_check("<NLP65883537E>", bool, preserve_input_text=preserve_input_text)
-    error.type_check("<NLP85452188E>", str, eos_token=eos_token)
+    error.type_check("<NLP85452188E>", str, allow_none=True, eos_token=eos_token)
     error.type_check(
         "<NLP03860681E>", int, allow_none=True, max_new_tokens=max_new_tokens
     )