diff --git a/src/css/defaultDisplay.js b/src/css/defaultDisplay.js
index 191fe1689..58ad1b0fb 100644
--- a/src/css/defaultDisplay.js
+++ b/src/css/defaultDisplay.js
@@ -4,7 +4,13 @@ define([
 ], function( jQuery ) {
 
 var iframe,
-	elemdisplay = {};
+	elemdisplay = {
+
+		// Support: Firefox
+		// We have to pre-define this values for FF (#10227)
+		HTML: "block",
+		BODY: "block"
+	};
 
 /**
  * Retrieve the actual display of a element