diff --git a/viper.go b/viper.go
index 7a49a0a..8a619ea 100644
--- a/viper.go
+++ b/viper.go
@@ -605,15 +605,35 @@ func (v *Viper) GetSizeInBytes(key string) uint {
 // Takes a single key and unmarshals it into a Struct
 func UnmarshalKey(key string, rawVal interface{}) error { return v.UnmarshalKey(key, rawVal) }
 func (v *Viper) UnmarshalKey(key string, rawVal interface{}) error {
-	return mapstructure.Decode(v.Get(key), rawVal)
+	config := &mapstructure.DecoderConfig{
+		Metadata:   nil,
+		Result:     rawVal,
+		DecodeHook: mapstructure.StringToTimeDurationHookFunc(),
+	}
+	decoder, err := mapstructure.NewDecoder(config)
+	if err != nil {
+		return err
+	}
+	return decoder.Decode(v.Get(key))
 }
 
 // Unmarshals the config into a Struct. Make sure that the tags
 // on the fields of the structure are properly set.
 func Unmarshal(rawVal interface{}) error { return v.Unmarshal(rawVal) }
 func (v *Viper) Unmarshal(rawVal interface{}) error {
-	err := mapstructure.WeakDecode(v.AllSettings(), rawVal)
+	config := &mapstructure.DecoderConfig{
+		Metadata:         nil,
+		Result:           rawVal,
+		WeaklyTypedInput: true,
+		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
+	}
 
+	decoder, err := mapstructure.NewDecoder(config)
+	if err != nil {
+		return err
+	}
+
+	err = decoder.Decode(v.AllSettings())
 	if err != nil {
 		return err
 	}
@@ -631,6 +651,7 @@ func weakDecodeExact(input, output interface{}) error {
 		Metadata:         nil,
 		Result:           output,
 		WeaklyTypedInput: true,
+		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
 	}
 
 	decoder, err := mapstructure.NewDecoder(config)
diff --git a/viper_test.go b/viper_test.go
index 858caff..b32c06a 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -453,10 +453,12 @@ func TestRecursiveAliases(t *testing.T) {
 func TestUnmarshal(t *testing.T) {
 	SetDefault("port", 1313)
 	Set("name", "Steve")
+	Set("duration", "10s")
 
 	type config struct {
-		Port int
-		Name string
+		Port     int
+		Name     string
+		Duration time.Duration
 	}
 
 	var C config
@@ -466,14 +468,15 @@ func TestUnmarshal(t *testing.T) {
 		t.Fatalf("unable to decode into struct, %v", err)
 	}
 
-	assert.Equal(t, &C, &config{Name: "Steve", Port: 1313})
+	assert.Equal(t, &config{Name: "Steve", Port: 1313, Duration: 10 * time.Second}, &C)
 
 	Set("port", 1234)
+	Set("duration", "20m")
 	err = Unmarshal(&C)
 	if err != nil {
 		t.Fatalf("unable to decode into struct, %v", err)
 	}
-	assert.Equal(t, &C, &config{Name: "Steve", Port: 1234})
+	assert.Equal(t, &config{Name: "Steve", Port: 1234, Duration: 20 * time.Minute}, &C)
 }
 
 func TestBindPFlags(t *testing.T) {