diff --git a/pkgs/development/python-modules/flax/default.nix b/pkgs/development/python-modules/flax/default.nix
index c176c825943c..098e6cf28e6b 100644
--- a/pkgs/development/python-modules/flax/default.nix
+++ b/pkgs/development/python-modules/flax/default.nix
@@ -1,7 +1,6 @@
 {
   lib,
   buildPythonPackage,
-  pythonOlder,
   fetchFromGitHub,
 
   # build-system
@@ -26,6 +25,7 @@
   pytest-xdist,
   pytestCheckHook,
   tensorflow,
+  treescope,
 
   # optional-dependencies
   matplotlib,
@@ -33,16 +33,14 @@
 
 buildPythonPackage rec {
   pname = "flax";
-  version = "0.8.5";
+  version = "0.9.0";
   pyproject = true;
 
-  disabled = pythonOlder "3.9";
-
   src = fetchFromGitHub {
     owner = "google";
     repo = "flax";
     rev = "refs/tags/v${version}";
-    hash = "sha256-6WOFq0758gtNdrlWqSQBlKmWVIGe5e4PAaGrvHoGjr0=";
+    hash = "sha256-iDWuUJKO7V4QrbVsS4ALgy6fbllOC43o7W4mhjtZ9xc=";
   };
 
   build-system = [
@@ -75,6 +73,7 @@ buildPythonPackage rec {
     pytest-xdist
     pytestCheckHook
     tensorflow
+    treescope
   ];
 
   pytestFlagsArray = [
@@ -95,13 +94,18 @@ buildPythonPackage rec {
     "flax/nnx/examples/*"
     # See https://github.com/google/flax/issues/3232.
     "tests/jax_utils_test.py"
-    # Requires tree
+    # Too old version of tensorflow:
+    # ModuleNotFoundError: No module named 'keras.api._v2'
     "tests/tensorboard_test.py"
   ];
 
   disabledTests = [
     # ValueError: Checkpoint path should be absolute
     "test_overwrite_checkpoints0"
+    # Fixed in more recent versions of jax: https://github.com/google/flax/issues/4211
+    # TODO: Re-enable when jax>0.4.28 will be available in nixpkgs
+    "test_vmap_and_cond_passthrough" # ValueError: vmap has mapped output but out_axes is None
+    "test_vmap_and_cond_passthrough_error" # AssertionError: "at vmap.*'broadcast'.*got axis spec ...
   ];
 
   meta = {