diff --git a/toolkit/components/history/src/nsGlobalHistory.cpp b/toolkit/components/history/src/nsGlobalHistory.cpp
index ede5344299ea..a004bf9bb544 100644
--- a/toolkit/components/history/src/nsGlobalHistory.cpp
+++ b/toolkit/components/history/src/nsGlobalHistory.cpp
@@ -1595,7 +1595,7 @@ nsGlobalHistory::GetSource(nsIRDFResource* aProperty,
     // XXX We could be more forgiving here, and check for literal
     // values as well.
     nsCOMPtr<nsIRDFResource> target = do_QueryInterface(aTarget);
-    if (IsURLInHistory(target))
+    if (target && IsURLInHistory(target))
       return CallQueryInterface(aTarget, aSource);
     
   }