diff --git a/annif/openapi/validation.py b/annif/openapi/validation.py
index 5cf4da392..ee541e344 100644
--- a/annif/openapi/validation.py
+++ b/annif/openapi/validation.py
@@ -22,7 +22,7 @@ def __init__(self, *args, **kwargs) -> None:
 
     def _validate(self, body: Any) -> dict | None:
         if not self._nullable and body is None:
-            raise BadRequestProblem("Request body must not be empty")
+            raise BadRequestProblem("Request body must not be empty")  # noqa
         try:
             return self._validator.validate(body)
         except ValidationError as exception: