diff --git a/library/core/src/char/methods.rs b/library/core/src/char/methods.rs
index b3af1f1ffb5..eb13e1f42bd 100644
--- a/library/core/src/char/methods.rs
+++ b/library/core/src/char/methods.rs
@@ -377,6 +377,8 @@ pub fn to_digit(self, radix: u32) -> Option<u32> {
     /// ```
     /// assert_eq!('❤'.escape_unicode().to_string(), "\\u{2764}");
     /// ```
+    #[must_use = "this returns the escaped char as an iterator, \
+                  without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn escape_unicode(self) -> EscapeUnicode {
@@ -453,6 +455,8 @@ pub(crate) fn escape_debug_ext(self, args: EscapeDebugExtArgs) -> EscapeDebug {
     /// ```
     /// assert_eq!('\n'.escape_debug().to_string(), "\\n");
     /// ```
+    #[must_use = "this returns the escaped char as an iterator, \
+                  without modifying the original"]
     #[stable(feature = "char_escape_debug", since = "1.20.0")]
     #[inline]
     pub fn escape_debug(self) -> EscapeDebug {
@@ -507,6 +511,8 @@ pub fn escape_debug(self) -> EscapeDebug {
     /// ```
     /// assert_eq!('"'.escape_default().to_string(), "\\\"");
     /// ```
+    #[must_use = "this returns the escaped char as an iterator, \
+                  without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn escape_default(self) -> EscapeDefault {