diff --git a/misc/fuel/factor-mode.el b/misc/fuel/factor-mode.el
index ed74af859b..b80ca4fbcf 100644
--- a/misc/fuel/factor-mode.el
+++ b/misc/fuel/factor-mode.el
@@ -253,7 +253,7 @@ source/docs/tests file. When set to false, you'll be asked only once."
   "^AFTER: +\\([^ ]+\\) +\\([^ ]+\\)")
 
 (defconst factor-integer-regex
-  "\\_<-?\\(0[xob]\\)?[0-9]+\\_>")
+  "\\_<-?[0-9]\\([xob][0-9a-fA-F]+\\|[0-9]*\\)?\\_>")
 
 (defconst factor-raw-float-regex
   "[0-9]*\\.[0-9]*\\([eEpP][+-]?[0-9]+\\)?")