diff --git a/src/Model/Migration.hs b/src/Model/Migration.hs
index 00feaee8c..e041bfd7b 100644
--- a/src/Model/Migration.hs
+++ b/src/Model/Migration.hs
@@ -653,7 +653,8 @@ customMigrations = Map.fromListWith (>>)
               let toAllocated :: [[PersistValue]] -> Maybe AllocationId
                   toAllocated = either (const Nothing) Just . fromPersistValue <=< listToMaybe <=< listToMaybe
               allocated <- toAllocated <$> sourceToList [queryQQ|SELECT "allocation_course".allocation FROM "allocation_deregister" INNER JOIN "allocation_course" ON "allocation_course".course = "allocation_deregister".course WHERE "user" = #{transactionUser} AND "allocation_course"."course" = #{transactionCourse} LIMIT 1;|]
-              [executeQQ|INSERT INTO "course_participant" ("course", "user", "registration", "state", "allocated") VALUES (#{transactionCourse}, #{transactionUser}, #{time}, #{CourseParticipantInactive False}, #{allocated}) ON CONFLICT DO NOTHING;|]
+              whenM (existsKey transactionCourse `and2M` existsKey transactionUser)
+                [executeQQ|INSERT INTO "course_participant" ("course", "user", "registration", "state", "allocated") VALUES (#{transactionCourse}, #{transactionUser}, #{time}, #{CourseParticipantInactive False}, #{allocated}) ON CONFLICT DO NOTHING;|]
             ensureParticipant _ = return ()
         runConduit $ getAuditLog .| C.mapM_ ensureParticipant
     )