diff --git a/USAGE.txt b/USAGE.txt
index 314b600536..2d636ce21c 100644
--- a/USAGE.txt
+++ b/USAGE.txt
@@ -64,6 +64,13 @@ Options:
         This is the same as Chromium's flag of the same name. Google it
         as the full description is too technical.
 
+    --quic-version=...
+
+        Forces a QUIC version. Allowed values: 39, 43, 46-49, or later.
+        See full definitions in quic_versions.h.
+
+        43 is the last version that works with Caddy's gQUIC.
+
     --log=[<path>]
 
         Saves log to the file at <path>. If <path> is empty, prints to