diff --git a/modules/docs.nix b/modules/docs.nix
index c9ab38d..377d35f 100644
--- a/modules/docs.nix
+++ b/modules/docs.nix
@@ -30,6 +30,11 @@ in
     enable = true;
     virtualHosts.":${toString port}".extraConfig = ''
       root * ${site}
+      # mdBook doesn't fingerprint asset filenames, so a browser left to its own
+      # heuristics caches the HTML and serves stale docs after a redeploy. Force a
+      # conditional request on every load; file_server's ETag/Last-Modified makes
+      # the unchanged case a cheap 304 over the mesh.
+      header Cache-Control "no-cache"
       file_server
     '';
   };