diff --git a/exporter.go b/exporter.go
index 4577730..c00a4a8 100644
--- a/exporter.go
+++ b/exporter.go
@@ -309,15 +309,16 @@ func (b *Exporter) Listen(e <-chan Events) {
 				}
 
 			case *TimerEvent:
-				timerType := ""
+				t := timerTypeDefault
 				if mapping != nil {
-					timerType = mapping.TimerType
+					t = mapping.TimerType
 				}
-				if timerType == "" {
-					timerType = b.mapper.Defaults.TimerType
+				if t == timerTypeDefault {
+					t = b.mapper.Defaults.TimerType
 				}
 
-				if timerType == "histogram" {
+				switch t {
+				case "histogram":
 					histogram, err := b.Histograms.Get(
 						b.suffix(metricName, "timer"),
 						prometheusLabels,
@@ -330,7 +331,8 @@ func (b *Exporter) Listen(e <-chan Events) {
 						log.Errorf(regErrF, metricName, err)
 						conflictingEventStats.WithLabelValues("timer").Inc()
 					}
-				} else {
+
+				case timerTypeDefault, timerTypeSummary:
 					summary, err := b.Summaries.Get(
 						b.suffix(metricName, "timer"),
 						prometheusLabels,
@@ -342,6 +344,9 @@ func (b *Exporter) Listen(e <-chan Events) {
 						log.Errorf(regErrF, metricName, err)
 						conflictingEventStats.WithLabelValues("timer").Inc()
 					}
+
+				default:
+					panic(fmt.Sprintf("unknown timer type '%s'", t))
 				}
 
 			default:
diff --git a/mapper.go b/mapper.go
index 9faaa75..4d1e172 100644
--- a/mapper.go
+++ b/mapper.go
@@ -35,7 +35,7 @@ var (
 )
 
 type mapperConfigDefaults struct {
-	TimerType string    `yaml:"timer_type"`
+	TimerType timerType `yaml:"timer_type"`
 	Buckets   []float64 `yaml:"buckets"`
 }
 
@@ -48,9 +48,9 @@ type metricMapper struct {
 type metricMapping struct {
 	Match     string `yaml:"match"`
 	regex     *regexp.Regexp
-	Labels    prometheus.Labels
-	TimerType string    `yaml:"timer_type"`
-	Buckets   []float64 `yaml:"buckets"`
+	Labels    prometheus.Labels `yaml:"labels"`
+	TimerType timerType         `yaml:"timer_type"`
+	Buckets   []float64         `yaml:"buckets"`
 }
 
 type configLoadStates int
@@ -126,13 +126,15 @@ func (m *metricMapper) initFromString(fileContents string) error {
 }
 
 func (m *metricMapper) initFromYAMLString(fileContents string) error {
-
 	var n metricMapper
 
+	fmt.Println(fileContents)
+
 	if err := yaml.Unmarshal([]byte(fileContents), &n); err != nil {
 		return err
 	}
 
+	fmt.Printf("%#v\n", n)
 	if n.Defaults.Buckets == nil || len(n.Defaults.Buckets) == 0 {
 		n.Defaults.Buckets = prometheus.DefBuckets
 	}
diff --git a/timer.go b/timer.go
new file mode 100644
index 0000000..8cf82d2
--- /dev/null
+++ b/timer.go
@@ -0,0 +1,41 @@
+// Copyright 2013 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import "fmt"
+
+type timerType string
+
+const (
+	timerTypeHistogram timerType = "histogram"
+	timerTypeSummary   timerType = "summary"
+	timerTypeDefault   timerType = ""
+)
+
+func (t *timerType) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var v string
+	if err := unmarshal(&v); err != nil {
+		return err
+	}
+
+	switch timerType(v) {
+	case timerTypeHistogram:
+		*t = timerTypeHistogram
+	case timerTypeSummary, timerTypeDefault:
+		*t = timerTypeSummary
+	default:
+		return fmt.Errorf("invalid timer type '%s'", v)
+	}
+	return nil
+}