diff --git a/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
index 1c10e9828d8..8967e826d3e 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
@@ -42,6 +42,7 @@
 #include "nsIDocShellTreeItem.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIWebBrowserChrome.h"
+#include "nsIInterfaceRequestor.h"
 #include "nsIDOMElement.h"
 
 #include "nsIDOMEventReceiver.h"