diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index e8cd93ba7dc..d42d2006cff 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -1535,7 +1535,7 @@ pub trait StrSlice<'a> {
     /// ```
     fn ends_with(&self, needle: &str) -> bool;
 
-    /// Returns a string with characters that match `to_trim` removed.
+    /// Returns a string with characters that match `to_trim` removed from the left and the right.
     ///
     /// # Arguments
     ///