diff --git a/libgrust/libproc_macro/rust/bridge/literal.rs b/libgrust/libproc_macro/rust/bridge/literal.rs
index b03e363db33..59825048970 100644
--- a/libgrust/libproc_macro/rust/bridge/literal.rs
+++ b/libgrust/libproc_macro/rust/bridge/literal.rs
@@ -1,12 +1,10 @@
 use bridge::{ffistring::FFIString, span::Span};
-use std::convert::TryInto;
-use std::ffi::c_uchar;
 use std::fmt;
 use std::str::FromStr;
 use LexError;
 
 extern "C" {
-    fn Literal__from_string(str: *const c_uchar, len: u64, lit: *mut Literal) -> bool;
+    fn Literal__from_string(str: FFIString, lit: *mut Literal) -> bool;
 }
 
 #[repr(C)]
@@ -234,13 +232,7 @@ impl FromStr for Literal {
         };
         // TODO: We might want to pass a LexError by reference to retrieve
         // error information
-        if unsafe {
-            Literal__from_string(
-                string.as_ptr(),
-                string.len().try_into().unwrap(),
-                &mut lit as *mut Literal,
-            )
-        } {
+        if unsafe { Literal__from_string(string.into(), &mut lit as *mut Literal) } {
             Err(LexError)
         } else {
             Ok(lit)
diff --git a/libgrust/libproc_macro/rust/bridge/token_stream.rs b/libgrust/libproc_macro/rust/bridge/token_stream.rs
index 79f161fce44..094f91f1370 100644
--- a/libgrust/libproc_macro/rust/bridge/token_stream.rs
+++ b/libgrust/libproc_macro/rust/bridge/token_stream.rs
@@ -1,6 +1,5 @@
-use bridge::{group::Group, ident::Ident, literal::Literal, punct::Punct};
+use bridge::{ffistring::FFIString, group::Group, ident::Ident, literal::Literal, punct::Punct};
 use std::convert::TryInto;
-use std::ffi::c_uchar;
 use std::fmt;
 use std::slice;
 use std::str::FromStr;
@@ -13,7 +12,7 @@ extern "C" {
     fn TokenStream__new() -> TokenStream;
     fn TokenStream__with_capacity(capacity: u64) -> TokenStream;
     fn TokenStream__push(stream: *mut TokenStream, tree: TokenTree);
-    fn TokenStream__from_string(str: *const c_uchar, len: u64, ts: *mut TokenStream) -> bool;
+    fn TokenStream__from_string(str: FFIString, ts: *mut TokenStream) -> bool;
     fn TokenStream__clone(ts: *const TokenStream) -> TokenStream;
     fn TokenStream__drop(stream: *mut TokenStream);
 }
@@ -136,13 +135,7 @@ impl FromStr for TokenStream {
     type Err = LexError;
     fn from_str(string: &str) -> Result<Self, LexError> {
         let mut ts = TokenStream::new();
-        if unsafe {
-            TokenStream__from_string(
-                string.as_ptr(),
-                string.len().try_into().unwrap(),
-                &mut ts as *mut TokenStream,
-            )
-        } {
+        if unsafe { TokenStream__from_string(string.into(), &mut ts as *mut TokenStream) } {
             Err(LexError)
         } else {
             Ok(ts)