diff --git a/pkg/mapper/mapper.go b/pkg/mapper/mapper.go
index 0f171655..69bcb087 100644
--- a/pkg/mapper/mapper.go
+++ b/pkg/mapper/mapper.go
@@ -43,7 +43,7 @@ var (
 
 type MetricMapper struct {
 	Registerer prometheus.Registerer
-	Defaults   mapperConfigDefaults `yaml:"defaults"`
+	Defaults   MapperConfigDefaults `yaml:"defaults"`
 	Mappings   []MetricMapping      `yaml:"mappings"`
 	FSM        *fsm.FSM
 	doFSM      bool
diff --git a/pkg/mapper/mapper_defaults.go b/pkg/mapper/mapper_defaults.go
index 754a677b..fea5f5e9 100644
--- a/pkg/mapper/mapper_defaults.go
+++ b/pkg/mapper/mapper_defaults.go
@@ -15,7 +15,7 @@ package mapper
 
 import "time"
 
-type mapperConfigDefaults struct {
+type MapperConfigDefaults struct {
 	ObserverType        ObserverType     `yaml:"observer_type"`
 	MatchType           MatchType        `yaml:"match_type"`
 	GlobDisableOrdering bool             `yaml:"glob_disable_ordering"`
@@ -39,7 +39,7 @@ type mapperConfigDefaultsAlias struct {
 
 // UnmarshalYAML is a custom unmarshal function to allow use of deprecated config keys
 // observer_type will override timer_type
-func (d *mapperConfigDefaults) UnmarshalYAML(unmarshal func(interface{}) error) error {
+func (d *MapperConfigDefaults) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	var tmp mapperConfigDefaultsAlias
 	if err := unmarshal(&tmp); err != nil {
 		return err