diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index dca8ffa4e2c89..c09f642d9696c 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -809,6 +809,7 @@ impl u8 {
         ascii::escape_default(self)
     }
 
+    #[inline]
     pub(crate) const fn is_utf8_char_boundary(self) -> bool {
         // This is bit magic equivalent to: b < 128 || b >= 192
         (self as i8) >= -0x40