diff --git a/utils.js b/utils.js
index 5ef23d6..167f184 100644
--- a/utils.js
+++ b/utils.js
@@ -208,6 +208,7 @@ common_scanmap[93]                 = 0xE05D; //KEY_Menu
 
 /* Firefox/Mozilla codes */
 var firefox_scanmap = [];
+firefox_scanmap[173]                = KEY_Minus;
 firefox_scanmap[109]                = KEY_Minus;
 firefox_scanmap[61]                 = KEY_Equal;
 firefox_scanmap[59]                 = KEY_SemiColon;