diff --git a/docs/releases/development.rst b/docs/releases/development.rst
index b95e61fd..470491ae 100644
--- a/docs/releases/development.rst
+++ b/docs/releases/development.rst
@@ -2,4 +2,5 @@
 Next release (in development)
 =============================
 
-* ...
+* Fix datasets hash_key generation when geometry encoding
+  is missing a dtype (:issue:`166`, :pr:`167`).
diff --git a/src/emsarray/conventions/_base.py b/src/emsarray/conventions/_base.py
index a6ced9b9..e35c38f1 100644
--- a/src/emsarray/conventions/_base.py
+++ b/src/emsarray/conventions/_base.py
@@ -1973,7 +1973,9 @@ def hash_geometry(self, hash: "hashlib._Hash") -> None:
             # Include the dtype of the data array.
             # A float array and an int array mean very different things,
             # but could have identical byte patterns.
-            hash_string(hash, data_array.encoding['dtype'].name)
+            # Checking for encoding dtype and falling back to values.dtype due to
+            # xarray multifile dataset bug - https://github.com/pydata/xarray/issues/2436
+            hash_string(hash, data_array.encoding.get('dtype', data_array.values.dtype).name)
 
             # Include the size and shape of the data.
             # 1D coordinate arrays are very different to 2D coordinate arrays,
diff --git a/tests/datasets/multifile_datasets/cfgrid2d/cfgrid2d_2024-01-01.nc b/tests/datasets/multifile_datasets/cfgrid2d/cfgrid2d_2024-01-01.nc
new file mode 100644
index 00000000..83fb6f69
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diff --git a/tests/datasets/multifile_datasets/cfgrid2d/cfgrid2d_2024-01-02.nc b/tests/datasets/multifile_datasets/cfgrid2d/cfgrid2d_2024-01-02.nc
new file mode 100644
index 00000000..4004959e
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diff --git a/tests/datasets/multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-01.nc b/tests/datasets/multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-01.nc
new file mode 100644
index 00000000..92f155de
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diff --git a/tests/datasets/multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-02.nc b/tests/datasets/multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-02.nc
new file mode 100644
index 00000000..b22e1612
Binary files /dev/null and b/tests/datasets/multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-02.nc differ
diff --git a/tests/operations/test_cache.py b/tests/operations/test_cache.py
index 7883ace4..48ae228e 100644
--- a/tests/operations/test_cache.py
+++ b/tests/operations/test_cache.py
@@ -2,6 +2,7 @@
 import pathlib
 
 import pytest
+import xarray
 
 import emsarray
 import emsarray.operations.cache
@@ -12,6 +13,8 @@
 int_hash = '7b08e025e311c3dfcf5179b67c0fdc08e73de261'
 attr_hash_lat = "2cb433979fc2d9c3884eea8569dd6a44406950f3"
 cache_key_hash_cf1d_sha1 = "2b006999273225ed70d4810357b6a06e6bebe9a6"
+cache_key_hash_multifile_cf2d_sha1 = "ea2d2e6131f1e499f622e83ed4fc2415649def06"
+cache_key_hash_multifile_ugrid_mesh2d_sha1 = "1d72e01b159135208324ae9a643166f85aecba27"
 
 # Blake2b
 cache_key_hash_cf1d = "1a3226072f08441ee79f727b0775709209ff2965299539c898ecc401cf17e23f"
@@ -200,3 +203,39 @@ def test_cache_key_cfgrid1d_sha1(datasets: pathlib.Path):
     assert result_cache_key_cf is not None
 
     assert result_cache_key_cf == cache_key_hash_cf1d_sha1
+
+
+def test_cache_key_with_multifile_dataset_ugrid_mesh2d(datasets: pathlib.Path):
+
+    ugrid_path1 = datasets / 'multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-01.nc'
+    ugrid_path2 = datasets / 'multifile_datasets/ugrid_mesh2d/ugrid_mesh2d_2024-01-02.nc'
+
+    dataset_paths = [ugrid_path1, ugrid_path2]
+
+    multifile_dataset = xarray.open_mfdataset(dataset_paths, data_vars=['values'])
+
+    multifile_ds_hash = hashlib.sha1()
+
+    multifile_dataset.ems.hash_geometry(multifile_ds_hash)
+
+    multifile_ds_digest = multifile_ds_hash.hexdigest()
+
+    assert multifile_ds_digest == cache_key_hash_multifile_ugrid_mesh2d_sha1
+
+
+def test_cache_key_with_multifile_dataset_cfgrid2d(datasets: pathlib.Path):
+
+    cfgrid_path1 = datasets / 'multifile_datasets/cfgrid2d/cfgrid2d_2024-01-01.nc'
+    cfgrid_path2 = datasets / 'multifile_datasets/cfgrid2d/cfgrid2d_2024-01-02.nc'
+
+    dataset_paths = [cfgrid_path1, cfgrid_path2]
+
+    multifile_dataset = xarray.open_mfdataset(dataset_paths, data_vars=['values'])
+
+    multifile_ds_hash = hashlib.sha1()
+
+    multifile_dataset.ems.hash_geometry(multifile_ds_hash)
+
+    multifile_ds_digest = multifile_ds_hash.hexdigest()
+
+    assert multifile_ds_digest == cache_key_hash_multifile_cf2d_sha1