diff --git a/skin/classic/treestyletab/base-colors.css b/skin/classic/treestyletab/base-colors.css
index 3713b616..6e611193 100644
--- a/skin/classic/treestyletab/base-colors.css
+++ b/skin/classic/treestyletab/base-colors.css
@@ -37,11 +37,11 @@
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
 :root[devtoolstheme="light"] {
-	--tabs-newtab-button-background:-moz-dialog;
-	--tabs-newtab-button-background-hover:ThreeDHighlight;
+	--tabs-newtab-button-background: -moz-dialog;
+	--tabs-newtab-button-background-hover: ThreeDHighlight;
 }
 
 :root[devtoolstheme="dark"] {
-	--tabs-newtab-button-background:#39424D;
-	--tabs-newtab-button-background-hover:#49525D;
+	--tabs-newtab-button-background: #39424D;
+	--tabs-newtab-button-background-hover: #49525D;
 }
\ No newline at end of file