diff --git a/library/core/src/char/decode.rs b/library/core/src/char/decode.rs
index 4784418f98c50..89e741a0c3e9c 100644
--- a/library/core/src/char/decode.rs
+++ b/library/core/src/char/decode.rs
@@ -122,7 +122,7 @@ impl<I: Iterator<Item = u16>> Iterator for DecodeUtf16<I> {
         let (low, high) = self.iter.size_hint();
         // we could be entirely valid surrogates (2 elements per
         // char), or entirely non-surrogates (1 element per char)
-        (low / 2, high)
+        (low.div_ceil(2), high)
     }
 }