diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 7aaf5a5fd4614..3b085b0459a4f 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -1208,7 +1208,8 @@ pub(crate) mod builtin {
     ///
     /// This macro has a second form, where a custom panic message can
     /// be provided with or without arguments for formatting. See [`std::fmt`]
-    /// for syntax for this form.
+    /// for syntax for this form. Expressions used as format arguments will only
+    /// be evaluated if the assertion fails.
     ///
     /// [`std::fmt`]: ../std/fmt/index.html
     ///
diff --git a/src/test/ui/macros/assert-format-lazy.rs b/src/test/ui/macros/assert-format-lazy.rs
new file mode 100644
index 0000000000000..c7f05d763b7a4
--- /dev/null
+++ b/src/test/ui/macros/assert-format-lazy.rs
@@ -0,0 +1,12 @@
+// run-pass
+// compile-flags: -C debug_assertions=yes
+
+#[allow(unreachable_code)]
+fn main() {
+    assert!(true, "Failed: {:?}", panic!("assert! evaluated format expressions"));
+    debug_assert!(true, "Failed: {:?}", panic!("debug_assert! evaluated format expressions"));
+    assert_eq!(1, 1, "Failed: {:?}", panic!("assert_eq! evaluated format expressions"));
+    debug_assert_eq!(1, 1, "Failed: {:?}", panic!("debug_assert_eq! evaluated format expressions"));
+    assert_ne!(1, 2, "Failed: {:?}", panic!("assert_ne! evaluated format expressions"));
+    debug_assert_ne!(1, 2, "Failed: {:?}", panic!("debug_assert_ne! evaluated format expressions"));
+}