diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index c27db0767ac..8057ff07591 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -1179,6 +1179,7 @@ pub fn xor(self, optb: Option<T>) -> Option<T> {
     /// *val = 3;
     /// assert_eq!(opt.unwrap(), 3);
     /// ```
+    #[must_use = "if you intended to set a value, consider assignment instead"]
     #[inline]
     #[stable(feature = "option_insert", since = "1.53.0")]
     pub fn insert(&mut self, value: T) -> &mut T {