Import from libcore where possible
diff --git a/src/rust_string.rs b/src/rust_string.rs
index f0d1df1..d10714b 100644
--- a/src/rust_string.rs
+++ b/src/rust_string.rs
@@ -1,4 +1,4 @@
-use std::mem;
+use core::mem;
 
 #[repr(C)]
 pub struct RustString {