diff --git a/models/helper.go b/models/helper.go
index 2868ad0..1f12a85 100644
--- a/models/helper.go
+++ b/models/helper.go
@@ -21,8 +21,10 @@ func QueryFilterByConceptDefsPlusCohortPairsHelper(sourceId int, mainCohortDefin
 	// Caching of temporary tables: for optimal performance, a temporary table dictionary / cache is updated, keeping a mapping
 	// of existing temporary table names vs underlying subsets of items in filterConceptDefsAndCohortPairs that gave rise to these
 	// tables.
-	finalSQL := "(SELECT subject_id FROM " + resultsDataSource.Schema + ".cohort WHERE cohort_definition_id=? )" + " as " + finalSetAlias + " "
-	query := resultsDataSource.Db.Table(finalSQL, mainCohortDefinitionId)
+	query := resultsDataSource.Db.Table(resultsDataSource.Schema+".cohort as "+finalSetAlias).
+		Select("*").
+		Where("cohort_definition_id=?", mainCohortDefinitionId)
+
 	tmpTableName := ""
 	for i, item := range filterConceptDefsAndCohortPairs {
 		tableAlias := fmt.Sprintf("filter_%d", i)
diff --git a/tests/models_tests/models_test.go b/tests/models_tests/models_test.go
index 3e521c3..76fdce8 100644
--- a/tests/models_tests/models_test.go
+++ b/tests/models_tests/models_test.go
@@ -790,7 +790,7 @@ func TestRetrieveHistogramDataBySourceIdAndCohortIdAndConceptDefsPlusCohortPairs
 	}
 	// everyone in the largestCohort has the histogramConceptId, but one person has NULL in the value_as_number:
 	if len(data) != largestCohort.CohortSize-1 {
-		t.Errorf("expected %d histogram data but got %d", largestCohort.CohortSize, len(data))
+		t.Errorf("expected %d histogram data but got %d", largestCohort.CohortSize-1, len(data))
 	}
 
 	// now filter on the extendedCopyOfSecondLargestCohort