diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index 193a1255..83bcee57 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -275,10 +275,10 @@ there will be called at other points of notmuch execution."
 (defface notmuch-message-summary-face
   `((((class color) (background light))
      ,@(and (>= emacs-major-version 27) '(:extend t))
-     (:background "#f0f0f0"))
+     :background "#f0f0f0")
     (((class color) (background dark))
      ,@(and (>= emacs-major-version 27) '(:extend t))
-     (:background "#303030")))
+     :background "#303030"))
   "Face for the single-line message summary in notmuch-show-mode."
   :group 'notmuch-show
   :group 'notmuch-faces)