diff --git a/viper.go b/viper.go
index 7027715..6d149f6 100644
--- a/viper.go
+++ b/viper.go
@@ -1743,7 +1743,7 @@ func (v *Viper) marshalWriter(f afero.File, configType string) error {
 			if sectionName == "default" {
 				sectionName = ""
 			}
-			cfg.Section(sectionName).Key(keyName).SetValue(v.Get(key).(string))
+			cfg.Section(sectionName).Key(keyName).SetValue(v.GetString(key))
 		}
 		cfg.WriteTo(f)
 	}