diff --git a/mo/imports.py b/mo/imports.py
index 2c7ceef5db10aa6c58ddc52393faedea1f689396..27e5a0992c1e194843a061f28a4d032c25beed6a 100644
--- a/mo/imports.py
+++ b/mo/imports.py
@@ -469,6 +469,7 @@ class ContestImport(Import):
 
     def setup(self):
         assert self.round is not None
+        assert not self.round.is_subround()
 
     def import_row(self, r: mo.csv.Row):
         assert isinstance(r, ContestImportRow)