diff --git a/mem0/vector_stores/redis.py b/mem0/vector_stores/redis.py
index 7fb1ada9e..3688927cd 100644
--- a/mem0/vector_stores/redis.py
+++ b/mem0/vector_stores/redis.py
@@ -192,9 +192,12 @@ class RedisDB(VectorStoreBase):
             "memory": payload["data"],
             "created_at": int(datetime.fromisoformat(payload["created_at"]).timestamp()),
             "updated_at": int(datetime.fromisoformat(payload["updated_at"]).timestamp()),
-            "embedding": np.array(vector, dtype=np.float32).tobytes(),
         }
 
+        # Only update embedding if vector is provided
+        if vector is not None:
+            data["embedding"] = np.array(vector, dtype=np.float32).tobytes()
+
         for field in ["agent_id", "run_id", "user_id"]:
             if field in payload:
                 data[field] = payload[field]
diff --git a/mem0/vector_stores/valkey.py b/mem0/vector_stores/valkey.py
index c4539dcd2..273aaba11 100644
--- a/mem0/vector_stores/valkey.py
+++ b/mem0/vector_stores/valkey.py
@@ -491,9 +491,12 @@ class ValkeyDB(VectorStoreBase):
                 "hash": payload.get("hash", f"hash_{vector_id}"),  # Use a default hash if not provided
                 "memory": payload.get("data", f"data_{vector_id}"),  # Use a default data if not provided
                 "created_at": int(datetime.fromisoformat(payload["created_at"]).timestamp()),
-                "embedding": np.array(vector, dtype=np.float32).tobytes(),
             }
 
+            # Only update embedding if vector is provided
+            if vector is not None:
+                hash_data["embedding"] = np.array(vector, dtype=np.float32).tobytes()
+
             # Add updated_at if available
             if "updated_at" in payload:
                 hash_data["updated_at"] = int(datetime.fromisoformat(payload["updated_at"]).timestamp())
diff --git a/tests/vector_stores/test_valkey.py b/tests/vector_stores/test_valkey.py
index 482f9b83d..65fa89fbb 100644
--- a/tests/vector_stores/test_valkey.py
+++ b/tests/vector_stores/test_valkey.py
@@ -204,6 +204,52 @@ def test_update_handles_missing_created_at(valkey_db, mock_valkey_client):
     assert "created_at" in kwargs["mapping"]  # Should be added automatically
 
 
+def test_update_with_none_vector_preserves_embedding(valkey_db, mock_valkey_client):
+    """Test that update with vector=None does not corrupt the stored embedding.
+
+    Regression test for #4336: when vector=None is passed (metadata-only update),
+    np.array(None) silently creates a 4-byte scalar, overwriting the real embedding.
+    The fix skips the embedding field entirely so the existing value is preserved.
+    """
+    payload = {
+        "hash": "test_hash",
+        "data": "updated_data",
+        "created_at": datetime.now(pytz.timezone("UTC")).isoformat(),
+        "user_id": "test_user",
+    }
+
+    valkey_db.update(vector_id="test_id", vector=None, payload=payload)
+
+    mock_valkey_client.hset.assert_called_once()
+    args, kwargs = mock_valkey_client.hset.call_args
+    assert "embedding" not in kwargs["mapping"], (
+        "embedding should not be in hash_data when vector is None"
+    )
+    assert kwargs["mapping"]["memory_id"] == "test_id"
+    assert kwargs["mapping"]["memory"] == "updated_data"
+
+
+def test_update_with_vector_includes_embedding(valkey_db, mock_valkey_client):
+    """Test that update with a real vector includes the embedding in hash_data."""
+    vector = np.random.rand(1536).tolist()
+    payload = {
+        "hash": "test_hash",
+        "data": "updated_data",
+        "created_at": datetime.now(pytz.timezone("UTC")).isoformat(),
+        "user_id": "test_user",
+    }
+
+    valkey_db.update(vector_id="test_id", vector=vector, payload=payload)
+
+    mock_valkey_client.hset.assert_called_once()
+    args, kwargs = mock_valkey_client.hset.call_args
+    assert "embedding" in kwargs["mapping"], (
+        "embedding should be in hash_data when vector is provided"
+    )
+    expected_bytes = np.array(vector, dtype=np.float32).tobytes()
+    assert kwargs["mapping"]["embedding"] == expected_bytes
+
+
 def test_get(valkey_db, mock_valkey_client):
     """Test getting a vector."""
     # Mock hgetall to return a vector