diff --git a/tests/controllers_tests/controllers_test.go b/tests/controllers_tests/controllers_test.go
index e7e4f2a..1381f79 100644
--- a/tests/controllers_tests/controllers_test.go
+++ b/tests/controllers_tests/controllers_test.go
@@ -81,6 +81,11 @@ func (h dummyCohortDataModel) RetrieveHistogramDataBySourceIdAndCohortIdAndConce
 	return cohortData, nil
 }
 
+func (h dummyCohortDataModel) RetrieveHistogramDataBySourceIdAndCohortIdAndConceptDefsPlusCohortPairs(sourceId int, cohortDefinitionId int, histogramConceptId int64, filterConceptDefsAndCohortPairs []interface{}) ([]*models.PersonConceptAndValue, error) {
+	cohortData := []*models.PersonConceptAndValue{}
+	return cohortData, nil
+}
+
 func (h dummyCohortDataModel) RetrieveHistogramDataBySourceIdAndConceptId(sourceId int, histogramConceptId int64) ([]*models.PersonConceptAndValue, error) {
 
 	cohortData := []*models.PersonConceptAndValue{}
@@ -907,13 +912,13 @@ func TestGetAttritionRowForConceptIdsAndCohortPairs(t *testing.T) {
 
 	// mix of concept ids and CustomDichotomousVariableDef items:
 	conceptIdsAndCohortPairs := []interface{}{
-		utils.CustomConceptVariableDef{ConceptId: int64(1234), ConceptValues: []int64{}},
-		utils.CustomConceptVariableDef{ConceptId: int64(5678), ConceptValues: []int64{}},
+		utils.CustomConceptVariableDef{ConceptId: int64(1234)},
+		utils.CustomConceptVariableDef{ConceptId: int64(5678)},
 		utils.CustomDichotomousVariableDef{
 			CohortDefinitionId1: 1,
 			CohortDefinitionId2: 2,
 			ProvidedName:        "testA12"},
-		utils.CustomConceptVariableDef{ConceptId: int64(2090006880), ConceptValues: []int64{}},
+		utils.CustomConceptVariableDef{ConceptId: int64(2090006880)},
 		utils.CustomDichotomousVariableDef{
 			CohortDefinitionId1: 3,
 			CohortDefinitionId2: 4,
diff --git a/tests/utils_tests/utils_test.go b/tests/utils_tests/utils_test.go
index 72ea77b..8384066 100644
--- a/tests/utils_tests/utils_test.go
+++ b/tests/utils_tests/utils_test.go
@@ -51,7 +51,7 @@ func TestParsePrefixedConceptIdsAndDichotomousIds(t *testing.T) {
 	requestContext.Writer = new(tests.CustomResponseWriter)
 	requestContext.Request = new(http.Request)
 	requestBody := "{\"variables\":[{\"variable_type\": \"concept\", \"concept_id\": 2000000324}," +
-		"{\"variable_type\": \"concept\", \"concept_id\": 2000000123, \"values\": [2000000237, 2000000238]}," +
+		"{\"variable_type\": \"concept\", \"concept_id\": 2000000123, \"filters\": [{\"type\": \"in\", \"values_as_concept_ids\": [2000000237, 2000000238]}]}," +
 		"{\"variable_type\": \"custom_dichotomous\", \"provided_name\": \"test\", \"cohort_ids\": [1, 3]}]}"
 	requestContext.Request.Body = io.NopCloser(strings.NewReader(requestBody))
 
@@ -60,9 +60,20 @@ func TestParsePrefixedConceptIdsAndDichotomousIds(t *testing.T) {
 		t.Errorf("Did not expect this request to abort")
 	}
 
-	expectedPrefixedConceptDefs := []utils.CustomConceptVariableDef{{ConceptId: 2000000324, ConceptValues: []int64{}}, {ConceptId: 2000000123, ConceptValues: []int64{2000000237, 2000000238}}}
+	expectedPrefixedConceptDefs := []utils.CustomConceptVariableDef{
+		{ConceptId: 2000000324},
+		{ConceptId: 2000000123,
+			Filters: []utils.Filter{
+				{
+					Type:               "in",
+					ValuesAsConceptIds: []int64{2000000237, 2000000238},
+				},
+			},
+		},
+	}
+
 	if !reflect.DeepEqual(conceptDefs, expectedPrefixedConceptDefs) {
-		t.Errorf("Expected %d but found %d", expectedPrefixedConceptDefs, conceptDefs)
+		t.Errorf("Expected %v but found %v", expectedPrefixedConceptDefs, conceptDefs)
 	}
 
 	expectedCohortPairs := []utils.CustomDichotomousVariableDef{
@@ -336,7 +347,7 @@ func TestGenerateStatsData(t *testing.T) {
 func TestConvertConceptIdToCustomConceptVariablesDef(t *testing.T) {
 	setUp(t)
 
-	expectedResult := []utils.CustomConceptVariableDef{{ConceptId: 1234, ConceptValues: []int64{}}, {ConceptId: 5678, ConceptValues: []int64{}}}
+	expectedResult := []utils.CustomConceptVariableDef{{ConceptId: 1234}, {ConceptId: 5678}}
 	conceptIds := []int64{1234, 5678}
 	result := utils.ConvertConceptIdToCustomConceptVariablesDef(conceptIds)
 
@@ -348,7 +359,17 @@ func TestConvertConceptIdToCustomConceptVariablesDef(t *testing.T) {
 func TestExtractConceptIdsFromCustomConceptVariablesDef(t *testing.T) {
 	setUp(t)
 
-	var testData = []utils.CustomConceptVariableDef{{ConceptId: 1234, ConceptValues: []int64{7890}}, {ConceptId: 5678, ConceptValues: []int64{}}}
+	var testData = []utils.CustomConceptVariableDef{
+		{ConceptId: 1234,
+			Filters: []utils.Filter{
+				{
+					Type:               "in",
+					ValuesAsConceptIds: []int64{7890},
+				},
+			},
+		},
+		{ConceptId: 5678},
+	}
 	expectedResult := []int64{1234, 5678}
 	result := utils.ExtractConceptIdsFromCustomConceptVariablesDef(testData)
 	if !reflect.DeepEqual(expectedResult, result) {
diff --git a/utils/parsing.go b/utils/parsing.go
index f7a389a..12f8a92 100644
--- a/utils/parsing.go
+++ b/utils/parsing.go
@@ -117,7 +117,7 @@ type Filter struct {
 	Value              *float64  `json:"value,omitempty"`
 	Values             []float64 `json:"values,omitempty"`
 	ValueAsConceptId   *int64    `json:"value_as_concept_id,omitempty"`
-	ValuesAsConceptIds []int64   `json:"values_as_concept_id,omitempty"`
+	ValuesAsConceptIds []int64   `json:"values_as_concept_ids,omitempty"`
 }
 
 // fields that define a custom dichotomous variable: