diff --git a/library/core/src/iter/adapters/map_windows.rs b/library/core/src/iter/adapters/map_windows.rs
index 0dada9eb6aacf..eead1f9e22e29 100644
--- a/library/core/src/iter/adapters/map_windows.rs
+++ b/library/core/src/iter/adapters/map_windows.rs
@@ -50,7 +50,7 @@ impl<I: Iterator, F, const N: usize> MapWindows<I, F, N> {
         assert!(N != 0, "array in `Iterator::map_windows` must contain more than 0 elements");
 
         // Only ZST arrays' length can be so large.
-        if size_of::<I::Item>() == 0 {
+        if size_of::<I::Item>() != 0 {
             assert!(
                 N.checked_mul(2).is_some(),
                 "array size of `Iterator::map_windows` is too large"