diff --git a/artiq/language/environment.py b/artiq/language/environment.py
index ce8a610ab..9f54bab15 100644
--- a/artiq/language/environment.py
+++ b/artiq/language/environment.py
@@ -175,6 +175,8 @@ class HasEnvironment:
 
         When the repository is scanned, any requested devices and arguments
         are set to ``None``.
+
+        Datasets are read-only in this method.
         """
         raise NotImplementedError