diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index dd8c7e9660a..3b29c257872 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -1526,7 +1526,7 @@ pub trait StrSlice for Sized? {
     /// ```
     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
     ///