diff --git a/aodntools/ncwriter/template.py b/aodntools/ncwriter/template.py
index 62c6c45..6742e0a 100644
--- a/aodntools/ncwriter/template.py
+++ b/aodntools/ncwriter/template.py
@@ -298,7 +298,7 @@ def create_variables(self, **kwargs):
 
         # variable attributes to convert to the same type as the variable
         # datatype
-        varattrs_to_convert_to_datatype = ['valid_min', 'valid_max', 'valid_range']
+        varattrs_to_convert_to_datatype = ['valid_min', 'valid_max', 'valid_range', 'flag_values']
 
         for varname, varattr in self.variables.items():
             if not varattr['_dimensions']:  # no kwargs in createVariable
diff --git a/setup.py b/setup.py
index 5ff7f23..baea0ec 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@
     'numpy>=2.2.4',
     'netCDF4>=1.7.2',
     'pandas>=2.2.3',
-    'xarray>=2023.1.0'
+    'xarray<=2025.3.1'
 ]
 
 TESTS_REQUIRE = [