diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index c4317799bcc68..88b84bd1352cc 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -132,9 +132,7 @@ iterator! {struct Iter -> *const T, &'a T, const, {/* no mut */}, {
         Self: Sized,
         F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
     {
-        self.as_slice().windows(2).all(|w| {
-            compare(&&w[0], &&w[1]).map(|o| o != Ordering::Greater).unwrap_or(false)
-        })
+        self.as_slice().is_sorted_by(|a, b| compare(&a, &b))
     }
 }}
 
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index d319b2bc37fdd..57b6e0ce4bb23 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -3822,7 +3822,7 @@ impl<T> [T] {
     where
         F: FnMut(&'a T, &'a T) -> Option<Ordering>,
     {
-        self.iter().is_sorted_by(|a, b| compare(*a, *b))
+        self.array_windows().all(|[a, b]| compare(a, b).map_or(false, Ordering::is_le))
     }
 
     /// Checks if the elements of this slice are sorted using the given key extraction function.