diff --git a/server/data_anndata/anndata_adaptor.py b/server/data_anndata/anndata_adaptor.py
index de0361ec..d71331c3 100644
--- a/server/data_anndata/anndata_adaptor.py
+++ b/server/data_anndata/anndata_adaptor.py
@@ -236,6 +236,14 @@ class AnndataAdaptor(DataAdaptor):
             warnings.warn(
                 f"Anndata data matrix is in {self.data.X.dtype} format not float32. " f"Precision may be truncated."
             )
+        if self.data.X.dtype < np.float32:
+            if self.data.isbacked:
+                raise DatasetAccessError(f"Data matrix in {self.data.X.dtype} format is not supported in backed mode."
+                                         " Please reload without --backed, or convert matrix to float32")
+            warnings.warn(
+                f"Anndata data matrix is in unsupported {self.data.X.dtype} format -- will be cast to float32"
+            )
+            self.data.X = self.data.X.astype(np.float32)
         for ax in Axis:
             curr_axis = getattr(self.data, str(ax))
             for ann in curr_axis:
diff --git a/test/fixtures/pbmc3k_16.h5ad b/test/fixtures/pbmc3k_16.h5ad
new file mode 100644
index 00000000..71aee9ee
Binary files /dev/null and b/test/fixtures/pbmc3k_16.h5ad differ
diff --git a/test/unit/data_anndata/test_anndata_adaptor.py b/test/unit/data_anndata/test_anndata_adaptor.py
index 3d54f0d5..f8ae8a86 100644
--- a/test/unit/data_anndata/test_anndata_adaptor.py
+++ b/test/unit/data_anndata/test_anndata_adaptor.py
@@ -1,5 +1,4 @@
 import json
-import sys
 import time
 import unittest
 
@@ -37,6 +36,7 @@ Test the anndata adaptor using the pbmc3k data set.
         (f"{FIXTURES_ROOT}/pbmc3k-CSC-gz.h5ad", True, "normal"),
         (f"{FIXTURES_ROOT}/pbmc3k-CSR-gz.h5ad", True, "normal"),
         (f"{FIXTURES_ROOT}/pbmc3k_64.h5ad", False, "auto"),  # 64 bit conversion tests
+        (f"{FIXTURES_ROOT}/pbmc3k_16.h5ad", False, "auto"),  # 16 bit conversion tests
     ],
 )
 class AdaptorTest(unittest.TestCase):
diff --git a/test/unit/data_anndata/test_anndata_adaptor_errors.py b/test/unit/data_anndata/test_anndata_adaptor_errors.py
new file mode 100644
index 00000000..8c3ed609
--- /dev/null
+++ b/test/unit/data_anndata/test_anndata_adaptor_errors.py
@@ -0,0 +1,23 @@
+import unittest
+
+from parameterized import parameterized_class
+
+from server.common.errors import DatasetAccessError
+from test import FIXTURES_ROOT
+from test.unit import app_config
+
+
+@parameterized_class(
+    ("data_locator", "backed", "X_approximate_distribution"),
+    [
+        (f"{FIXTURES_ROOT}/pbmc3k_16.h5ad", True, "auto"),  # 16 bit conversion tests
+    ],
+)
+class AdaptorLoadErrorTest(unittest.TestCase):
+    def test_float16_backed_raises_err(self):
+        with self.assertRaises(DatasetAccessError):
+            config = app_config(
+                self.data_locator,
+                backed=self.backed,
+                extra_dataset_config=dict(X_approximate_distribution=self.X_approximate_distribution),
+            )