diff --git a/extensions/cookie/nsPermissionManager.cpp b/extensions/cookie/nsPermissionManager.cpp
index 99a3f769c096..71af2ffc40ea 100644
--- a/extensions/cookie/nsPermissionManager.cpp
+++ b/extensions/cookie/nsPermissionManager.cpp
@@ -87,7 +87,11 @@ nsresult
 GetOriginFromPrincipal(nsIPrincipal* aPrincipal, nsACString& aOrigin)
 {
   nsresult rv = aPrincipal->GetOriginNoSuffix(aOrigin);
-  NS_ENSURE_SUCCESS(rv, rv);
+  // The principal may belong to the about:blank content viewer, so this can be
+  // expected to fail.
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
 
   nsAutoCString suffix;
   rv = aPrincipal->GetOriginSuffix(suffix);