diff --git a/_CoqProject b/_CoqProject
index ca14c2b5ea1acb14e6dad4d107c8595bd354e8b3..04559153ccd1c7a0d593cef86d980525d8859208 100644
--- a/_CoqProject
+++ b/_CoqProject
@@ -1,10 +1,15 @@
 -Q theories lrust
-# We sometimes want to locally override notation and there is no good way to do that with scopes.
+# We sometimes want to locally override notation (e.g. in proofmode/base.v, bi/embedding.v), and there
+# is no good way to do that with scopes.
 -arg -w -arg -notation-overridden
 # non-canonical projections (https://github.com/coq/coq/pull/10076) do not exist yet in 8.9.
 -arg -w -arg -redundant-canonical-projection
 # change_no_check does not exist yet in 8.9.
 -arg -w -arg -convert_concl_no_check
+# "Declare Scope" does not exist yet in 8.9.
+-arg -w -arg -undeclared-scope
+# We have ambiguous paths and so far it is not even clear what they are (https://gitlab.mpi-sws.org/iris/iris/issues/240).
+-arg -w -arg -ambiguous-paths
 
 theories/lifetime/model/definitions.v
 theories/lifetime/model/faking.v