diff --git a/library/std/src/io/buffered/bufreader/buffer.rs b/library/std/src/io/buffered/bufreader/buffer.rs
index 5251cc302cb49..9fd2472ebdfdb 100644
--- a/library/std/src/io/buffered/bufreader/buffer.rs
+++ b/library/std/src/io/buffered/bufreader/buffer.rs
@@ -109,8 +109,8 @@ impl Buffer {
 
     /// Read more bytes into the buffer without discarding any of its contents
     pub fn read_more(&mut self, mut reader: impl Read) -> io::Result<usize> {
-        let mut buf = BorrowedBuf::from(&mut self.buf[self.pos..]);
-        let old_init = self.initialized - self.pos;
+        let mut buf = BorrowedBuf::from(&mut self.buf[self.filled..]);
+        let old_init = self.initialized - self.filled;
         unsafe {
             buf.set_init(old_init);
         }