diff --git a/mypy/options.py b/mypy/options.py
index f18457526b57..6963fa883c2b 100644
--- a/mypy/options.py
+++ b/mypy/options.py
@@ -76,6 +76,7 @@ class BuildType:
         "strict_bytes",
         "fixed_format_cache",
         "untyped_calls_exclude",
+        "enable_incomplete_feature",  # Added to ensure cache is invalidated when this flag changes
     }
 ) - {"debug_cache"}