diff --git a/.github/workflows/tests-studio.yml b/.github/workflows/tests-studio.yml
index 456becf7f..e6ba4fe4d 100644
--- a/.github/workflows/tests-studio.yml
+++ b/.github/workflows/tests-studio.yml
@@ -98,7 +98,7 @@ jobs:
       - name: Run tests
         # Generate `.test_durations` file with `pytest --store-durations --durations-path ../.github/.test_durations ...`
         run: >
-          DATACHAIN_METASTORE_ARG_PROJECT=john
+          DATACHAIN_METASTORE_ARG_USERNAME=john
           PYTHONPATH="$(pwd)/..:${PYTHONPATH}"
           pytest
           --config-file=pyproject.toml -rs
diff --git a/src/datachain/dataset.py b/src/datachain/dataset.py
index 085e82903..9ed813313 100644
--- a/src/datachain/dataset.py
+++ b/src/datachain/dataset.py
@@ -32,7 +32,7 @@
 LISTING_PREFIX = "lst__"
 
 DEFAULT_DATASET_VERSION = "1.0.0"
-DATASET_NAME_RESERVED_CHARS = ["."]
+DATASET_NAME_RESERVED_CHARS = [".", "@"]
 DATASET_NAME_REPLACEMENT_CHAR = "_"
 
 
diff --git a/src/datachain/namespace.py b/src/datachain/namespace.py
index 3200c3630..86010568b 100644
--- a/src/datachain/namespace.py
+++ b/src/datachain/namespace.py
@@ -6,7 +6,7 @@
 from datachain.error import InvalidNamespaceNameError
 
 N = TypeVar("N", bound="Namespace")
-NAMESPACE_NAME_RESERVED_CHARS = ["."]
+NAMESPACE_NAME_RESERVED_CHARS = [".", "@"]
 
 
 @dataclass(frozen=True)
diff --git a/src/datachain/project.py b/src/datachain/project.py
index af8d14a9b..fad77ead2 100644
--- a/src/datachain/project.py
+++ b/src/datachain/project.py
@@ -7,7 +7,7 @@
 from datachain.namespace import Namespace
 
 P = TypeVar("P", bound="Project")
-PROJECT_NAME_RESERVED_CHARS = ["."]
+PROJECT_NAME_RESERVED_CHARS = [".", "@"]
 
 
 @dataclass(frozen=True)