diff --git a/library/std/src/sys/stdio/windows.rs b/library/std/src/sys/stdio/windows.rs
index 475a0592528b4..89976847d3817 100644
--- a/library/std/src/sys/stdio/windows.rs
+++ b/library/std/src/sys/stdio/windows.rs
@@ -278,7 +278,7 @@ impl io::Read for Stdin {
             Ok(bytes_copied)
         } else if buf.len() - bytes_copied < 4 {
             // Not enough space to get a UTF-8 byte. We will use the incomplete UTF8.
-            let mut utf16_buf = [MaybeUninit::new(0); 1];
+            let mut utf16_buf = [MaybeUninit::new(0); 2];
             // Read one u16 character.
             let read = read_u16s_fixup_surrogates(handle, &mut utf16_buf, 1, &mut self.surrogate)?;
             // Read bytes, using the (now-empty) self.incomplete_utf8 as extra space.