diff --git a/conda-env/ci.yml b/conda-env/ci.yml
index 7df34b39b..ab4792909 100644
--- a/conda-env/ci.yml
+++ b/conda-env/ci.yml
@@ -4,7 +4,6 @@
 name: e3sm_diags_ci
 channels:
   - conda-forge
-  - defaults
 dependencies:
   # Base
   # =================
@@ -15,7 +14,7 @@ dependencies:
   - cartopy >=0.17.0
   - cartopy_offlinedata
   - cf-units
-  - dask <2024.12.0
+  - dask !=2024.12.0,!=2024.12.1
   - lxml
   - mache >=0.15.0
   - matplotlib-base >=3.8.2
diff --git a/conda-env/dev.yml b/conda-env/dev.yml
index 8c009787d..3196b2233 100644
--- a/conda-env/dev.yml
+++ b/conda-env/dev.yml
@@ -2,7 +2,6 @@
 name: e3sm_diags_dev
 channels:
   - conda-forge
-  - defaults
 dependencies:
   # Base
   # =======================
@@ -13,7 +12,7 @@ dependencies:
   - cartopy >=0.17.0
   - cartopy_offlinedata
   - cf-units
-  - dask <2024.12.0
+  - dask !=2024.12.0,!=2024.12.1
   - lxml
   - mache >=0.15.0
   - matplotlib-base >=3.8.2
diff --git a/pyproject.toml b/pyproject.toml
index d4c85c1ea..cb611503e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,7 +33,7 @@ dependencies = [
   # This package is not available on PyPI.
   # "cartopy_offlinedata",
   "cf-units",
-  "dask <2024.12.0",
+  "dask !=2024.12.0,!=2024.12.1",
   "lxml",
   "mache >=0.15.0",
   "matplotlib >=3.8.2",
@@ -50,12 +50,7 @@ dependencies = [
 [project.optional-dependencies]
 test = ["pytest", "pytest-cov"]
 docs = ["sphinx", "sphinx_rtd_theme", "sphinx-multiversion"]
-dev = [
-  "pre-commit",
-  "types-PyYAML",
-  "ruff",
-  "mypy",
-]
+dev = ["pre-commit", "types-PyYAML", "ruff", "mypy"]
 
 [project.urls]
 Documentation = "https://docs.e3sm.org/e3sm_diags/_build/html/main/index.html"