diff --git a/library/core/src/iter/adapters/chain.rs b/library/core/src/iter/adapters/chain.rs
index 60eb3a6da3a4b..1e2fccd8780c2 100644
--- a/library/core/src/iter/adapters/chain.rs
+++ b/library/core/src/iter/adapters/chain.rs
@@ -1,4 +1,4 @@
-use crate::iter::{DoubleEndedIterator, FusedIterator, Iterator, TrustedLen};
+use crate::iter::{DoubleEndedIterator, ExactSizeIterator, FusedIterator, Iterator, TrustedLen};
 use crate::ops::Try;
 
 /// An iterator that links two iterators together, in a chain.
@@ -282,6 +282,13 @@ where
 {
 }
 
+impl<A, B> ExactSizeIterator for Chain<A, B>
+where
+    A: ExactSizeIterator,
+    B: ExactSizeIterator,
+{
+}
+
 #[inline]
 fn and_then_or_clear<T, U>(opt: &mut Option<T>, f: impl FnOnce(&mut T) -> Option<U>) -> Option<U> {
     let x = f(opt.as_mut()?);