diff --git a/vmoe/projects/contrastive/evaluators.py b/vmoe/projects/contrastive/evaluators.py
index 11ee1d9..7e0623a 100644
--- a/vmoe/projects/contrastive/evaluators.py
+++ b/vmoe/projects/contrastive/evaluators.py
@@ -57,6 +57,12 @@ def __init__(
     if bv_discriminative is None:
       raise NotImplementedError(
           'Big Vision must be installed to run the discriminative evaluation.')
+    if (
+        not hasattr(data_sharding.mesh, 'devices')
+        or data_sharding.mesh.devices is None
+    ):
+      raise ValueError(
+          'data_sharding.mesh must be a Mesh, not an AbstractMesh.')
     bv_evaluator = bv_discriminative.Evaluator(
         predict_fn=apply_fn,
         devices=list(data_sharding.mesh.devices.flatten()),
@@ -120,6 +126,12 @@ def __init__(
     if bv_retrieval is None:
       raise NotImplementedError(
           'Big Vision must be installed to run the retrieval evaluation.')
+    if (
+        not hasattr(data_sharding.mesh, 'devices')
+        or data_sharding.mesh.devices is None
+    ):
+      raise ValueError(
+          'data_sharding.mesh must be a Mesh, not an AbstractMesh.')
     bv_evaluator = bv_retrieval.Evaluator(
         predict_fn=apply_fn,
         devices=list(data_sharding.mesh.devices.flatten()),