Import prelude types explicitly from alloc
diff --git a/src/cxx_string.rs b/src/cxx_string.rs
index 5780e3e..2c712f1 100644
--- a/src/cxx_string.rs
+++ b/src/cxx_string.rs
@@ -1,4 +1,5 @@
 use alloc::borrow::Cow;
+use alloc::string::String;
 use core::fmt::{self, Debug, Display};
 use core::slice;
 use core::str::{self, Utf8Error};