diff --git a/library/core/src/char/mod.rs b/library/core/src/char/mod.rs
index a860c7c6aaadc..bf9f633eef370 100644
--- a/library/core/src/char/mod.rs
+++ b/library/core/src/char/mod.rs
@@ -339,6 +339,7 @@ impl Iterator for EscapeDebug {
         }
     }
 
+    #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
         let n = self.len();
         (n, Some(n))