diff --git a/README.md b/README.md
index 288d9dee..f0199bac 100644
--- a/README.md
+++ b/README.md
@@ -228,6 +228,8 @@ RNFS.readDir(RNFS.MainBundlePath) // On Android, use "RNFS.DocumentDirectoryPath
 var RNFS = require('react-native-fs');
 
 // create a path you want to write to
+// :warning: on iOS, you cannot write into `RNFS.MainBundlePath`, 
+// but `RNFS.DocumentDirectoryPath` exists on both platforms and is writable
 var path = RNFS.DocumentDirectoryPath + '/test.txt';
 
 // write the file