diff --git a/tests/goth_tests/assertions.py b/tests/goth_tests/assertions.py
index b63318662..69c19c891 100644
--- a/tests/goth_tests/assertions.py
+++ b/tests/goth_tests/assertions.py
@@ -24,14 +24,14 @@ async def assert_no_errors(output_lines: EventStream[str]):
 
 async def assert_all_invoices_accepted(output_lines: EventStream[str]):
     """Assert that an invoice is accepted for every provider that confirmed an agreement."""
-    unpaid_agreement_providers = set()
+    unpaid_agreement_providers = list()
 
     async for line in output_lines:
         m = re.search("Agreement confirmed by provider '([^']*)'", line)
         if m:
             prov_name = m.group(1)
             logger.debug("assert_all_invoices_accepted: adding provider '%s'", prov_name)
-            unpaid_agreement_providers.add(prov_name)
+            unpaid_agreement_providers.append(prov_name)
         m = re.search("Accepted invoice from '([^']*)'", line)
         if m:
             prov_name = m.group(1)