diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 681dfda4ad517..dc7637cfdb934 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -2642,7 +2642,7 @@ impl str {
     /// # Panics
     ///
     /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is
-    /// beyond the last code point of the string slice.
+    /// past the end of the last code point of the string slice.
     ///
     /// # Examples
     ///
@@ -2683,7 +2683,7 @@ impl str {
     /// # Panics
     ///
     /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is
-    /// beyond the last code point of the string slice.
+    /// past the end of the last code point of the string slice.
     ///
     /// # Examples
     ///