diff --git a/docs/source/command_line.rst b/docs/source/command_line.rst
index b1505d7d9668..49b8a71fb85b 100644
--- a/docs/source/command_line.rst
+++ b/docs/source/command_line.rst
@@ -1027,6 +1027,10 @@ beyond what incremental mode can offer, try running mypy in
 
     Include fine-grained dependency information in the cache for the mypy daemon.
 
+.. option:: --fixed-format-cache
+
+    Use new fast and compact fixed format cache.
+
 .. option:: --skip-version-check
 
     By default, mypy will ignore cache data generated by a different