diff --git a/conda-environment.yml b/conda-environment.yml
index 11dd58f7521..248e4dd21c0 100644
--- a/conda-environment.yml
+++ b/conda-environment.yml
@@ -9,7 +9,7 @@ dependencies:
   - graphviz  # for static graphing
   # Note: can't pin jinja2 any higher than this until we give up on Cylc 7 back-compat
   - jinja2 >=3.0,<3.1
-  - metomi-isodatetime >=1!3.0.0, <1!3.1.0
+  - metomi-isodatetime >=1!3.0.0, <1!3.2.0
   # Constrain protobuf version for compatible Scheduler-UIS comms across hosts
   - protobuf >=4.21.2,<4.22.0
   - psutil >=5.6.0
diff --git a/setup.cfg b/setup.cfg
index fbac4552f57..2229d24a007 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -67,7 +67,7 @@ install_requires =
     graphene>=2.1,<3
     # Note: can't pin jinja2 any higher than this until we give up on Cylc 7 back-compat
     jinja2==3.0.*
-    metomi-isodatetime==1!3.0.*
+    metomi-isodatetime>=1!3.0.0,<1!3.2.0
     # Constrain protobuf version for compatible Scheduler-UIS comms across hosts
     protobuf>=4.21.2,<4.22.0
     psutil>=5.6.0