diff --git a/runtime/query.go b/runtime/query.go
index 69f0ba1d6a7..4b031219c1f 100644
--- a/runtime/query.go
+++ b/runtime/query.go
@@ -48,8 +48,11 @@ func populateFieldValueFromPath(msg proto.Message, fieldPath []string, values []
 			return fmt.Errorf("non-aggregate type in the mid of path: %s", strings.Join(fieldPath, "."))
 		}
 		var f reflect.Value
-		f, props = fieldByProtoName(m, fieldName)
-		if !f.IsValid() {
+		var err error
+		f, props, err = fieldByProtoName(m, fieldName)
+		if err != nil {
+			return err
+		} else if !f.IsValid() {
 			grpclog.Printf("field not found in %T: %s", msg, strings.Join(fieldPath, "."))
 			return nil
 		}
@@ -92,14 +95,26 @@ func populateFieldValueFromPath(msg proto.Message, fieldPath []string, values []
 
 // fieldByProtoName looks up a field whose corresponding protobuf field name is "name".
 // "m" must be a struct value. It returns zero reflect.Value if no such field found.
-func fieldByProtoName(m reflect.Value, name string) (reflect.Value, *proto.Properties) {
+func fieldByProtoName(m reflect.Value, name string) (reflect.Value, *proto.Properties, error) {
 	props := proto.GetProperties(m.Type())
+
+	// look up field name in oneof map
+	if op, ok := props.OneofTypes[name]; ok {
+		v := reflect.New(op.Type.Elem())
+		field := m.Field(op.Field)
+		if !field.IsNil() {
+			return reflect.Value{}, nil, fmt.Errorf("field already set for %s oneof", props.Prop[op.Field].OrigName)
+		}
+		field.Set(v)
+		return v.Elem().Field(0), op.Prop, nil
+	}
+
 	for _, p := range props.Prop {
 		if p.OrigName == name {
-			return m.FieldByName(p.Name), p
+			return m.FieldByName(p.Name), p, nil
 		}
 	}
-	return reflect.Value{}, nil
+	return reflect.Value{}, nil, nil
 }
 
 func populateRepeatedField(f reflect.Value, values []string, props *proto.Properties) error {
diff --git a/runtime/query_test.go b/runtime/query_test.go
index 82026a8ed84..07262fad67f 100644
--- a/runtime/query_test.go
+++ b/runtime/query_test.go
@@ -161,7 +161,7 @@ func TestPopulateParameters(t *testing.T) {
 			},
 			filter:  utilities.NewDoubleArray(nil),
 			want:    &proto3Message{},
-			wanterr: errors.New("field already set for oneof"),
+			wanterr: errors.New("field already set for oneof_value oneof"),
 		},
 	} {
 		msg := proto.Clone(spec.want)