diff --git a/ci/recipe/meta.yaml b/ci/recipe/meta.yaml
index d564f841e..64995e8a7 100644
--- a/ci/recipe/meta.yaml
+++ b/ci/recipe/meta.yaml
@@ -32,7 +32,7 @@ requirements:
     - lxml
     - mache >=1.11.0
     - matplotlib-base >=3.9.0
-    - mpas_tools >=0.34.0
+    - mpas_tools >=0.34.1,<1.0.0
     - nco >=4.8.1,!=5.2.6
     - netcdf4
     - numpy >=2.0,<3.0
diff --git a/dev-spec.txt b/dev-spec.txt
index 8e6f362fe..dfeb22413 100644
--- a/dev-spec.txt
+++ b/dev-spec.txt
@@ -15,7 +15,7 @@ gsw
 lxml
 mache >=1.11.0
 matplotlib-base>=3.9.0
-mpas_tools>=0.34.1
+mpas_tools>=0.34.1,<1.0.0
 nco>=4.8.1,!=5.2.6
 netcdf4
 numpy>=2.0,<3.0