diff --git a/fava.nix b/fava.nix
index 4abc344..f9958ef 100644
--- a/fava.nix
+++ b/fava.nix
@@ -5,10 +5,17 @@ with lib;
 let
   cfg = config.services.fava;
 
-  # Build fava with extensions included in its Python environment
+  # Build fava with extensions included in its Python environment.
+  # Extensions that depend on fava are overridden to remove it from their
+  # dependencies, avoiding duplicate package conflicts in the closure.
+  stripFavaDep = ext: ext.overridePythonAttrs (old: {
+    dependencies = builtins.filter (dep: (dep.pname or "") != "fava") (old.dependencies or []);
+  });
+
   favaWithExtensions = if cfg.extensions == [] then cfg.package else
     cfg.package.overridePythonAttrs (old: {
-      propagatedBuildInputs = (old.propagatedBuildInputs or []) ++ cfg.extensions;
+      dependencies = (old.dependencies or []) ++ map stripFavaDep cfg.extensions;
+      dontCheckForDuplicates = true;
     });
 
 in {