diff --git a/pkgs/applications/office/fava/default.nix b/pkgs/applications/office/fava/default.nix
index 822ef3da2216..ce6988e6e61b 100644
--- a/pkgs/applications/office/fava/default.nix
+++ b/pkgs/applications/office/fava/default.nix
@@ -10,7 +10,14 @@ python3.pkgs.buildPythonApplication rec {
     sha256 = "sha256-Uw8UIJa+Dtsy+o31I1ynLyhZrFNX42NFRXu1O2ISbzU=";
   };
 
-  pythonRelaxDeps = [ "cheroot" ];
+  patches = [
+    ./flask-babel.patch
+  ];
+
+  pythonRelaxDeps = [
+    "cheroot"
+    "Flask-Babel"
+  ];
 
   nativeBuildInputs = with python3.pkgs; [ setuptools-scm pythonRelaxDepsHook ];
 
diff --git a/pkgs/applications/office/fava/flask-babel.patch b/pkgs/applications/office/fava/flask-babel.patch
new file mode 100644
index 000000000000..739be6327ca8
--- /dev/null
+++ b/pkgs/applications/office/fava/flask-babel.patch
@@ -0,0 +1,14 @@
+diff --git a/src/fava/application.py b/src/fava/application.py
+index 811c1de4..19de051a 100644
+--- a/src/fava/application.py
++++ b/src/fava/application.py
+@@ -148,8 +148,7 @@ def get_locale() -> str | None:
+     return request.accept_languages.best_match(["en"] + LANGUAGES)
+ 
+ 
+-BABEL = Babel(app)
+-BABEL.localeselector(get_locale)
++BABEL = Babel(app, locale_selector=get_locale)
+ 
+ 
+ for function in template_filters.FILTERS: