--- a/mail/base/content/hiddenWindow.xhtml
+++ b/mail/base/content/hiddenWindow.xhtml
@@ -17,16 +17,20 @@
 <!ENTITY % baseMenuOverlayDTD SYSTEM "chrome://messenger/locale/baseMenuOverlay.dtd">
 %baseMenuOverlayDTD;
 <!ENTITY % charsetDTD SYSTEM "chrome://global/locale/charsetMenu.dtd">
 %charsetDTD;
 <!ENTITY % viewZoomOverlayDTD SYSTEM "chrome://messenger/locale/viewZoomOverlay.dtd">
 %viewZoomOverlayDTD;
 <!ENTITY % msgReadSMIMEDTD SYSTEM "chrome://messenger-smime/locale/msgReadSMIMEOverlay.dtd">
 %msgReadSMIMEDTD;
+#ifdef MOZ_OPENPGP
+<!ENTITY % bondOpenPGPDTD SYSTEM "chrome://openpgp/content/strings/bond.dtd">
+%bondOpenPGPDTD;
+#endif
 <!ENTITY % quickFilterBarDTD SYSTEM "chrome://messenger/locale/quickFilterBar.dtd">
 %quickFilterBarDTD;
 <!ENTITY % msgViewPickerDTD SYSTEM "chrome://messenger/locale/msgViewPickerOverlay.dtd" >
 %msgViewPickerDTD;
 <!ENTITY % msgHdrViewOverlayDTD SYSTEM "chrome://messenger/locale/msgHdrViewOverlay.dtd">
 %msgHdrViewOverlayDTD;
 <!ENTITY % lightningDTD SYSTEM "chrome://lightning/locale/lightning.dtd">
 %lightningDTD;