diff --git a/browser/themes/gnomestripe/browser/preferences/preferences.css b/browser/themes/gnomestripe/browser/preferences/preferences.css
index 681805d8e47..0ddf6dfe2ca 100644
--- a/browser/themes/gnomestripe/browser/preferences/preferences.css
+++ b/browser/themes/gnomestripe/browser/preferences/preferences.css
@@ -132,11 +132,11 @@ filefield {
 }
 
 filefield[disabled="true"] .fileFieldContentBox {
-  -moz-opacity: 0.5;
+  opacity: 0.5;
 }
 
 filefield[disabled="true"] .fileFieldIcon {
-  -moz-opacity: 0.2;
+  opacity: 0.2;
 }
 
 .fileFieldIcon {
diff --git a/browser/themes/winstripe/browser/preferences/preferences.css b/browser/themes/winstripe/browser/preferences/preferences.css
index e304d9d6e92..acb8e078e76 100644
--- a/browser/themes/winstripe/browser/preferences/preferences.css
+++ b/browser/themes/winstripe/browser/preferences/preferences.css
@@ -130,11 +130,11 @@ filefield {
 }
 
 filefield[disabled="true"] .fileFieldContentBox {
-  -moz-opacity: 0.5;
+  opacity: 0.5;
 }
 
 filefield[disabled="true"] .fileFieldIcon {
-  -moz-opacity: 0.2;
+  opacity: 0.2;
 }
 
 .fileFieldIcon {