diff --git a/src/main/scala/beam/utils/csv/writers/PopulationCsvWriter.scala b/src/main/scala/beam/utils/csv/writers/PopulationCsvWriter.scala
index 3ad2ff084d9..f3e366dc1a9 100755
--- a/src/main/scala/beam/utils/csv/writers/PopulationCsvWriter.scala
+++ b/src/main/scala/beam/utils/csv/writers/PopulationCsvWriter.scala
@@ -44,7 +44,7 @@ object PopulationCsvWriter extends ScenarioCsvWriter {
         person.getId.toString,
         customAttributes.age.getOrElse(""),
         !customAttributes.isMale,
-        personIdToHouseHoldId(person.getId),
+        personIdToHouseHoldId.get(person.getId).map(_.toString).getOrElse(""),
         String.valueOf(personAttributes.getAttribute(person.getId.toString, "rank")),
         excludedModes
       )