diff --git a/accessible/src/generic/DocAccessible.cpp b/accessible/src/generic/DocAccessible.cpp
index 530e782911aa..8d71148702e9 100644
--- a/accessible/src/generic/DocAccessible.cpp
+++ b/accessible/src/generic/DocAccessible.cpp
@@ -85,7 +85,8 @@ DocAccessible::
   mPresShell(aPresShell)
 {
   mFlags |= eDocAccessible;
-  mPresShell->SetAccDocument(this);
+  if (mPresShell)
+    mPresShell->SetAccDocument(this);
 
   mDependentIDsHash.Init();
   // XXX aaronl should we use an algorithm for the initial cache size?