diff --git a/basyx/aas/adapter/http.py b/basyx/aas/adapter/http.py
index 7b5f6854e..e55fddff3 100644
--- a/basyx/aas/adapter/http.py
+++ b/basyx/aas/adapter/http.py
@@ -380,7 +380,7 @@ def to_python(self, value: str) -> model.Identifier:
         except binascii.Error:
             raise BadRequest(f"Encoded identifier {value} is invalid base64url!")
         except UnicodeDecodeError:
-            raise BadRequest(f"Encoded base64url value is not a valid utf-8 string!")
+            raise BadRequest(f"Encoded base64url value is not a valid {self.encoding} string!")
         return decoded