diff --git browser/themes/shared/devtools/common.css browser/themes/shared/devtools/common.css
index a8208dc..df70486 100644
--- browser/themes/shared/devtools/common.css
+++ browser/themes/shared/devtools/common.css
@@ -11,13 +11,13 @@
 .devtools-monospace {
 %ifdef XP_MACOSX
   font-family: Menlo, monospace;
-%endif
-%ifdef XP_LINUX
+%elifdef XP_WIN
+  font-family: Consolas, monospace;
+%else
   font-family: monospace;
-  font-size: 80%;
 %endif
-%ifdef XP_WIN
-  font-family: Consolas, monospace;
+%if defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_QT)
+  font-size: 80%;
 %endif
 }
 
@@ -62,7 +62,7 @@
   background-image: linear-gradient(to bottom, hsla(209,18%,18%,0.9), hsl(210,11%,16%));
   border-radius: 3px;
   overflow-x: hidden;
-%ifdef XP_LINUX
+%if defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_QT)
   max-height: 32rem;
 %else
   max-height: 40rem;
diff --git browser/themes/shared/devtools/highlighter.inc.css browser/themes/shared/devtools/highlighter.inc.css
index 5b881b5..050f78b 100644
--- browser/themes/shared/devtools/highlighter.inc.css
+++ browser/themes/shared/devtools/highlighter.inc.css
@@ -54,7 +54,7 @@ html|*.highlighter-nodeinfobar-pseudo-classes {
   padding: 0;
   width: 26px;
   min-height: 26px;
-%ifndef XP_LINUX
+%if !defined(MOZ_WIDGET_GTK) && !defined(MOZ_WIDGET_QT)
   background-color: transparent;
 %endif
 }