diff --git a/src/libcollections/fmt.rs b/src/libcollections/fmt.rs
index b095b8131b644..883417e9f4ec7 100644
--- a/src/libcollections/fmt.rs
+++ b/src/libcollections/fmt.rs
@@ -327,7 +327,7 @@
 //! format := '{' [ argument ] [ ':' format_spec ] '}'
 //! argument := integer | identifier
 //!
-//! format_spec := [[fill]align][sign]['#'][0][width]['.' precision][type]
+//! format_spec := [[fill]align][sign]['#']['0'][width]['.' precision][type]
 //! fill := character
 //! align := '<' | '^' | '>'
 //! sign := '+' | '-'