diff --git a/src/datadoc/backend/model_validation.py b/src/datadoc/backend/model_validation.py
index 075414c4..04cc5378 100644
--- a/src/datadoc/backend/model_validation.py
+++ b/src/datadoc/backend/model_validation.py
@@ -146,7 +146,7 @@ def check_obligatory_variables_metadata(self) -> Self:
                     num_obligatory_variable_fields_completed(
                         v,
                     )
-                    != OBLIGATORY_VARIABLES_METADATA_IDENTIFIERS
+                    != len(OBLIGATORY_VARIABLES_METADATA_IDENTIFIERS)
                 ):
                     warnings.warn(
                         f"{OBLIGATORY_METADATA_WARNING} {get_missing_obligatory_variables_fields(self.variables)}",