diff --git a/src/nomad_simulations/schema_packages/general.py b/src/nomad_simulations/schema_packages/general.py
index 8fa5d75e..d38de349 100644
--- a/src/nomad_simulations/schema_packages/general.py
+++ b/src/nomad_simulations/schema_packages/general.py
@@ -309,7 +309,7 @@ def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
         # Finding which is the representative system of a calculation: typically, we will
         # define it as the last system reported (TODO CHECK THIS!).
         # TODO extend adding the proper representative system extraction using `normalizer.py`
-        if self.model_system is None:
+        if not self.model_system:
             logger.error('No system information reported.')
             return
         system_ref = self.model_system[-1]