diff --git a/misc/factor.el b/misc/factor.el
index 72fdf64159..2afb5a7b7f 100644
--- a/misc/factor.el
+++ b/misc/factor.el
@@ -103,6 +103,7 @@
     (" !.*$" . font-lock-comment-face)
     ("( .* )" . font-lock-comment-face)
     ("\"[^ ][^\"]*\"" . font-lock-string-face)
+    ("\"\"" . font-lock-string-face)
     ("\\(P\\|SBUF\\)\"" 1 font-lock-keyword-face)
     ,@(mapcar #'(lambda (w) (cons (concat "\\(^\\| \\)\\(" w "\\)\\($\\| \\)")
                              '(2 font-lock-keyword-face)))