diff --git a/pkg/ffapi/filter.go b/pkg/ffapi/filter.go
index 69e6708..f8ac8c9 100644
--- a/pkg/ffapi/filter.go
+++ b/pkg/ffapi/filter.go
@@ -426,6 +426,8 @@ func (f *baseFilter) Finalize() (fi *FilterInfo, err error) {
 	var values []FieldSerialization
 	var mods []FieldMod
 
+	resolvedField := f.field
+
 	switch f.op {
 	case FilterOpAnd, FilterOpOr:
 		children = make([]*FilterInfo, len(f.children))
@@ -437,11 +439,11 @@ func (f *baseFilter) Finalize() (fi *FilterInfo, err error) {
 	case FilterOpIn, FilterOpNotIn:
 		fValues := f.value.([]driver.Value)
 		values = make([]FieldSerialization, len(fValues))
-		name := strings.ToLower(f.field)
-		field, ok := f.fb.queryFields[name]
+		name, field, ok := f.fb.queryFields.Resolve(f.field)
 		if !ok {
-			return nil, i18n.NewError(f.fb.ctx, i18n.MsgInvalidFilterField, name)
+			return nil, i18n.NewError(f.fb.ctx, i18n.MsgInvalidFilterField, f.field)
 		}
+		resolvedField = name
 		mods = fieldMods(field)
 		for i, fv := range fValues {
 			values[i] = field.GetSerialization()
@@ -450,11 +452,11 @@ func (f *baseFilter) Finalize() (fi *FilterInfo, err error) {
 			}
 		}
 	default:
-		name := strings.ToLower(f.field)
-		field, ok := f.fb.queryFields[name]
+		name, field, ok := f.fb.queryFields.Resolve(f.field)
 		if !ok {
-			return nil, i18n.NewError(f.fb.ctx, i18n.MsgInvalidFilterField, name)
+			return nil, i18n.NewError(f.fb.ctx, i18n.MsgInvalidFilterField, f.field)
 		}
+		resolvedField = name
 		mods = fieldMods(field)
 		skipScan := false
 		switch f.value.(type) {
@@ -505,7 +507,7 @@ func (f *baseFilter) Finalize() (fi *FilterInfo, err error) {
 	return &FilterInfo{
 		Children:       children,
 		Op:             f.op,
-		Field:          f.field,
+		Field:          resolvedField,
 		FieldMods:      mods,
 		Values:         values,
 		Value:          value,
@@ -525,9 +527,9 @@ func (fb *filterBuilder) Sort(fields ...string) FilterBuilder {
 			field = strings.TrimPrefix(field, "-")
 			descending = true
 		}
-		if _, ok := fb.queryFields[field]; ok {
+		if name, _, ok := fb.queryFields.Resolve(field); ok {
 			fb.sort = append(fb.sort, &SortField{
-				Field:      field,
+				Field:      name,
 				Descending: descending,
 			})
 		}
@@ -542,8 +544,8 @@ func (f *baseFilter) Sort(fields ...string) Filter {
 
 func (fb *filterBuilder) GroupBy(fields ...string) FilterBuilder {
 	for _, field := range fields {
-		if _, ok := fb.queryFields[field]; ok {
-			fb.groupBy = append(fb.groupBy, field)
+		if name, _, ok := fb.queryFields.Resolve(field); ok {
+			fb.groupBy = append(fb.groupBy, name)
 		}
 	}
 	return fb
@@ -556,8 +558,8 @@ func (f *baseFilter) GroupBy(fields ...string) Filter {
 
 func (fb *filterBuilder) RequiredFields(fields ...string) FilterBuilder {
 	for _, field := range fields {
-		if _, ok := fb.queryFields[field]; ok {
-			fb.requiredFields = append(fb.requiredFields, field)
+		if name, _, ok := fb.queryFields.Resolve(field); ok {
+			fb.requiredFields = append(fb.requiredFields, name)
 		}
 	}
 	return fb
diff --git a/pkg/ffapi/filter_test.go b/pkg/ffapi/filter_test.go
index 4607350..15c15af 100644
--- a/pkg/ffapi/filter_test.go
+++ b/pkg/ffapi/filter_test.go
@@ -373,3 +373,63 @@ func TestValueFilterAccess(t *testing.T) {
 	assert.Equal(t, "seq", fb.ValueFilter().Field())
 	assert.Equal(t, 12345, fb.ValueFilter().Value())
 }
+
+// caseTestFactory declares camelCase fields, which resolve only if lookups fold case.
+var caseTestFactory = &QueryFields{
+	"id":            &Int64Field{},
+	"parentAccount": &StringField{},
+	"effectiveTime": &TimeField{},
+}
+
+func TestFilterFieldAnyCase(t *testing.T) {
+	for _, spelling := range []string{"parentAccount", "parentaccount", "PARENTACCOUNT"} {
+		fb := caseTestFactory.NewFilter(context.Background())
+		fi, err := fb.Eq(spelling, "urn:kld:account=abc").Finalize()
+		assert.NoError(t, err)
+		assert.Equal(t, "parentAccount", fi.Field, "Eq %q", spelling)
+
+		fb = caseTestFactory.NewFilter(context.Background())
+		fi, err = fb.In(spelling, []driver.Value{"a", "b"}).Finalize()
+		assert.NoError(t, err)
+		assert.Equal(t, "parentAccount", fi.Field, "In %q", spelling)
+	}
+}
+
+func TestFilterFieldAnyCaseUnknown(t *testing.T) {
+	fb := caseTestFactory.NewFilter(context.Background())
+	_, err := fb.Eq("NoSuchField", "value").Finalize()
+	assert.Regexp(t, "FF00142.*NoSuchField", err)
+
+	fb = caseTestFactory.NewFilter(context.Background())
+	_, err = fb.In("NoSuchField", []driver.Value{"a"}).Finalize()
+	assert.Regexp(t, "FF00142.*NoSuchField", err)
+}
+
+func TestSortGroupByAnyCase(t *testing.T) {
+	fb := caseTestFactory.NewFilter(context.Background())
+	fi, err := fb.Eq("id", 1).
+		Sort("-effectivetime", "PARENTACCOUNT").
+		GroupBy("parentaccount").
+		RequiredFields("EFFECTIVETIME").
+		Finalize()
+	assert.NoError(t, err)
+	assert.Equal(t, "effectiveTime", fi.Sort[0].Field)
+	assert.True(t, fi.Sort[0].Descending)
+	assert.Equal(t, "parentAccount", fi.Sort[1].Field)
+	assert.False(t, fi.Sort[1].Descending)
+	assert.Equal(t, []string{"parentAccount"}, fi.GroupBy)
+	assert.Equal(t, []string{"effectiveTime"}, fi.RequiredFields)
+}
+
+func TestSortGroupByUnknownDropped(t *testing.T) {
+	fb := caseTestFactory.NewFilter(context.Background())
+	fi, err := fb.Eq("id", 1).
+		Sort("nosuchfield").
+		GroupBy("nosuchfield").
+		RequiredFields("nosuchfield").
+		Finalize()
+	assert.NoError(t, err)
+	assert.Empty(t, fi.Sort)
+	assert.Empty(t, fi.GroupBy)
+	assert.Empty(t, fi.RequiredFields)
+}
diff --git a/pkg/ffapi/query_fields.go b/pkg/ffapi/query_fields.go
index 27d4146..864df49 100644
--- a/pkg/ffapi/query_fields.go
+++ b/pkg/ffapi/query_fields.go
@@ -72,6 +72,20 @@ func (qf QueryFields) NewUpdate(ctx context.Context) UpdateBuilder {
 	}
 }
 
+// Resolve looks up a field by name, falling back to a case-insensitive match when there is no exact
+// one. The returned name is the one declared in the map.
+func (qf QueryFields) Resolve(fieldAnyCase string) (string, Field, bool) {
+	if f, ok := qf[fieldAnyCase]; ok {
+		return fieldAnyCase, f, true
+	}
+	for name, f := range qf {
+		if strings.EqualFold(name, fieldAnyCase) {
+			return name, f, true
+		}
+	}
+	return "", nil, false
+}
+
 func (qf QueryFields) Clone() QueryFields {
 	qf2 := make(QueryFields, len(qf))
 	for n, f := range qf {