diff --git a/src/header/map.rs b/src/header/map.rs
index 7e7e9ca6..1f93b22c 100644
--- a/src/header/map.rs
+++ b/src/header/map.rs
@@ -16,7 +16,7 @@ pub use self::into_header_name::IntoHeaderName;
 
 /// A set of HTTP headers
 ///
-/// `HeaderMap` is an multimap of [`HeaderName`] to values.
+/// `HeaderMap` is a multimap of [`HeaderName`] to values.
 ///
 /// [`HeaderName`]: struct.HeaderName.html
 ///