diff --git a/neural_lam/config.py b/neural_lam/config.py
index 349ffd9..ada00a9 100644
--- a/neural_lam/config.py
+++ b/neural_lam/config.py
@@ -87,7 +87,7 @@ class TrainingConfig:
     ] = dataclasses.field(default_factory=UniformFeatureWeighting)
 
     logger: str = "wandb"
-    logger_url: str = None
+    logger_url: str = ""
 
 
 @dataclasses.dataclass
diff --git a/tests/test_config.py b/tests/test_config.py
index ede6b24..ec8b00e 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -45,7 +45,7 @@ def test_config_serialization(state_weighting_config):
   config_path: ""
 training:
   logger: wandb
-  logger_url: https://wandb.ai
+  logger_url: ""
   state_feature_weighting:
     __config_class__: ManualStateFeatureWeighting
     weights: