diff --git a/mu4e/mu4e-headers.el b/mu4e/mu4e-headers.el
index 65265e77..f45d7b4a 100644
--- a/mu4e/mu4e-headers.el
+++ b/mu4e/mu4e-headers.el
@@ -1381,7 +1381,7 @@ query (effectively, 'widen' it), with `mu4e-headers-query-prev'."
   (unless mu4e~headers-last-query
     (mu4e-warn "There's nothing to filter"))
   (mu4e-headers-search
-    (format "(%s) AND %s" mu4e~headers-last-query filter)))
+    (format "(%s) AND (%s)" mu4e~headers-last-query filter)))
 
 
 (defun mu4e-headers-change-sorting (&optional field dir)
diff --git a/mu4e/mu4e.texi b/mu4e/mu4e.texi
index 4ce797fd..3a4cb9ff 100644
--- a/mu4e/mu4e.texi
+++ b/mu4e/mu4e.texi
@@ -2021,7 +2021,7 @@ asks for an additional search pattern, which is appended to the current search
 query, in effect getting you the subset of the currently shown headers that
 also match this extra search pattern. @key{\} takes you back to the previous
 query, so, effectively 'widens' the search. Technically, narrowing the results
-of query @t{x} with expression @t{y} implies doing a search @t{(x) AND y}.
+of query @t{x} with expression @t{y} implies doing a search @t{(x) AND (y)}.
 
 Note that messages that were not in your original search results because
 of @code{mu4e-headers-results-limit} may show up in the narrowed query.