diff --git a/viper.go b/viper.go
index 4f1580c..b77e682 100644
--- a/viper.go
+++ b/viper.go
@@ -865,27 +865,13 @@ func UnmarshalKey(key string, rawVal interface{}, opts ...DecoderConfigOption) e
 	return v.UnmarshalKey(key, rawVal, opts...)
 }
 func (v *Viper) UnmarshalKey(key string, rawVal interface{}, opts ...DecoderConfigOption) error {
-	lcaseKey := strings.ToLower(key)
+	err := decode(v.Get(key), defaultDecoderConfig(rawVal, opts...))
 
-	// AllSettings returns settings from every sources merged into one tree
-	settings := v.AllSettings()
-
-	keyParts := strings.Split(lcaseKey, v.keyDelim)
-	for i := 0; i < len(keyParts)-1; i++ {
-		if value, found := settings[keyParts[i]]; found {
-			if valueMap, ok := value.(map[string]interface{}); ok {
-				settings = valueMap
-				continue
-			}
-			// if the current value is not a map[string]interface{} we most likely reach a
-			// leaf and the key/path is wrong
-			return fmt.Errorf("unknown key %s", lcaseKey)
-		} else {
-			return fmt.Errorf("unknown key %s", lcaseKey)
-		}
+	if err != nil {
+		return err
 	}
-	finalSetting := settings[keyParts[len(keyParts)-1]]
-	return decode(finalSetting, defaultDecoderConfig(rawVal, opts...))
+
+	return nil
 }
 
 // Unmarshal unmarshals the config into a Struct. Make sure that the tags
diff --git a/viper_test.go b/viper_test.go
index f41b413..5507a6d 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -1703,48 +1703,6 @@ func TestParseNested(t *testing.T) {
 	assert.Equal(t, 200*time.Millisecond, items[0].Nested.Delay)
 }
 
-func TestUnmarshalKey(t *testing.T) {
-	type testStruct struct {
-		Delay int      `mapstructure:"delay" yaml:"delay"`
-		Port  int      `mapstructure:"port" yaml:"port"`
-		Host  string   `mapstructure:"host" yaml:"host"`
-		Items []string `mapstructure:"items" yaml:"items"`
-	}
-
-	config := `
-level_1:
-  level_2:
-    port: 1234
-    items:
-      - "test 1"
-`
-	v := New()
-	v.SetDefault("level_1.level_2.delay", 50)
-	v.SetDefault("level_1.level_2.port", 9999)
-	v.SetDefault("level_1.level_2.host", "default")
-	v.SetDefault("level_1.level_2.items", []string{})
-
-	// Use env vars for some settings
-	v.BindEnv("level_1.level_2.host", "DD_TEST_HOST")
-	t.Setenv("DD_TEST_HOST", "dd.com")
-
-	initConfig(v, "yaml", config)
-
-	// manually overwrite some settings
-	v.Set("level_1.level_2.items", []string{"test_2", "test_3"})
-
-	data := testStruct{}
-	err := v.UnmarshalKey("level_1.level_2", &data)
-	if err != nil {
-		t.Fatalf("unable to decode into struct, %v", err)
-	}
-
-	assert.Equal(t, 50, data.Delay)                           // value from defaults
-	assert.Equal(t, 1234, data.Port)                          // value from config
-	assert.Equal(t, "dd.com", data.Host)                      // value from env
-	assert.Equal(t, []string{"test_2", "test_3"}, data.Items) // value from Set()
-}
-
 func doTestCaseInsensitive(t *testing.T, typ, config string) {
 	v := New()
 	initConfig(v, typ, config)