diff --git a/pkgs/development/python-modules/dask/default.nix b/pkgs/development/python-modules/dask/default.nix
index af46945b5197..47bf61b9db09 100644
--- a/pkgs/development/python-modules/dask/default.nix
+++ b/pkgs/development/python-modules/dask/default.nix
@@ -32,6 +32,7 @@
   pytest-cov-stub,
   pytest-mock,
   pytest-rerunfailures,
+  pytest-timeout,
   pytest-xdist,
   pytestCheckHook,
   versionCheckHook,
@@ -39,14 +40,14 @@
 
 buildPythonPackage rec {
   pname = "dask";
-  version = "2025.11.0";
+  version = "2025.12.0";
   pyproject = true;
 
   src = fetchFromGitHub {
     owner = "dask";
     repo = "dask";
     tag = version;
-    hash = "sha256-cU4w4dqJQ3ew+fRyD7Lc4URNfW738kKqls6k6j65pIo=";
+    hash = "sha256-oGBOt2ULLn0Kx1rOVNWaC3l1ECotMC2yNeCHya9Tx+s=";
   };
 
   build-system = [
@@ -94,6 +95,7 @@ buildPythonPackage rec {
     pytest-cov-stub
     pytest-mock
     pytest-rerunfailures
+    pytest-timeout
     pytest-xdist
     pytestCheckHook
     versionCheckHook
diff --git a/pkgs/development/python-modules/ome-zarr/default.nix b/pkgs/development/python-modules/ome-zarr/default.nix
index 67a14ed7a03a..78f854f744b7 100644
--- a/pkgs/development/python-modules/ome-zarr/default.nix
+++ b/pkgs/development/python-modules/ome-zarr/default.nix
@@ -57,6 +57,11 @@ buildPythonPackage rec {
   disabledTests = [
     # attempts to access network
     "test_s3_info"
+
+    # AssertionError: assert {'blocksize':... 'blosc', ...} == {'blocksize':... 'blosc', ...}
+    # comp {'id': 'blosc', 'cname': 'lz4', 'clevel': 5, 'shuffle': 1, 'blocksize': 0}
+    "test_default_compression"
+    "test_write_image_compressed"
   ];
 
   disabledTestPaths = [