diff --git a/src/ensure.rs b/src/ensure.rs
index 423e164..a919ed3 100644
--- a/src/ensure.rs
+++ b/src/ensure.rs
@@ -1,4 +1,5 @@
 use crate::Error;
+use alloc::string::String;
 use core::fmt::{self, Debug, Write};
 use core::mem::MaybeUninit;
 use core::ptr;