diff --git a/core/dbt/deprecations.py b/core/dbt/deprecations.py
index 114af126ea0..08ff8862c65 100644
--- a/core/dbt/deprecations.py
+++ b/core/dbt/deprecations.py
@@ -138,7 +138,7 @@ def cb():
     return cb
 
 
-def warn(name, *args, **kwargs):
+def warn(name: str, *args, **kwargs) -> None:
     if name not in deprecations:
         # this should (hopefully) never happen
         raise RuntimeError("Error showing deprecation warning: {}".format(name))