diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 72ad7c244eeba..9fbfd92eaf883 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -304,7 +304,7 @@ pub struct DirBuilder {
 pub fn read<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
     fn inner(path: &Path) -> io::Result<Vec<u8>> {
         let mut file = File::open(path)?;
-        let size = file.metadata().map(|m| m.len() as usize).ok();
+        let size = file.metadata().map(|m| usize::try_from(m.len()).unwrap_or(usize::MAX)).ok();
         let mut bytes = Vec::try_with_capacity(size.unwrap_or(0))?;
         io::default_read_to_end(&mut file, &mut bytes, size)?;
         Ok(bytes)
@@ -346,7 +346,7 @@ pub fn read<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
 pub fn read_to_string<P: AsRef<Path>>(path: P) -> io::Result<String> {
     fn inner(path: &Path) -> io::Result<String> {
         let mut file = File::open(path)?;
-        let size = file.metadata().map(|m| m.len() as usize).ok();
+        let size = file.metadata().map(|m| usize::try_from(m.len()).unwrap_or(usize::MAX)).ok();
         let mut string = String::new();
         string.try_reserve_exact(size.unwrap_or(0))?;
         io::default_read_to_string(&mut file, &mut string, size)?;