diff --git a/mozilla/suite/themes/classic/navigator/mac/tabbrowser.css b/mozilla/suite/themes/classic/navigator/mac/tabbrowser.css
index 874c1df0c57..c71ce616c6a 100644
--- a/mozilla/suite/themes/classic/navigator/mac/tabbrowser.css
+++ b/mozilla/suite/themes/classic/navigator/mac/tabbrowser.css
@@ -7,6 +7,10 @@
   -moz-border-bottom-colors: ThreeDDarkShadow ThreeDShadow;
 }
 
+tabpanels {
+  -moz-appearance: none;
+}
+
 .tabbrowser-tabs {
   padding-top: 1px;
 }
diff --git a/mozilla/suite/themes/classic/navigator/win/tabbrowser.css b/mozilla/suite/themes/classic/navigator/win/tabbrowser.css
index 874c1df0c57..c71ce616c6a 100644
--- a/mozilla/suite/themes/classic/navigator/win/tabbrowser.css
+++ b/mozilla/suite/themes/classic/navigator/win/tabbrowser.css
@@ -7,6 +7,10 @@
   -moz-border-bottom-colors: ThreeDDarkShadow ThreeDShadow;
 }
 
+tabpanels {
+  -moz-appearance: none;
+}
+
 .tabbrowser-tabs {
   padding-top: 1px;
 }