--- a/embedding/components/printingui/ipc/nsPrintingProxy.cpp
+++ b/embedding/components/printingui/ipc/nsPrintingProxy.cpp
@@ -221,21 +221,19 @@ nsPrintingProxy::AllocPPrintProgressDial
   NS_NOTREACHED("Allocator for PPrintProgressDialogChild should not be "
                 "called on nsPrintingProxy.");
   return nullptr;
 }
 
 bool
 nsPrintingProxy::DeallocPPrintProgressDialogChild(PPrintProgressDialogChild* aActor)
 {
-  // The parent process will never initiate the PPrintProgressDialog
-  // protocol connection, so no need to provide an deallocator here.
-  NS_NOTREACHED("Deallocator for PPrintProgressDialogChild should not be "
-                "called on nsPrintingProxy.");
-  return false;
+  // The PrintProgressDialogChild implements refcounting, and
+  // will take itself out.
+  return true;
 }
 
 PPrintSettingsDialogChild*
 nsPrintingProxy::AllocPPrintSettingsDialogChild()
 {
   // The parent process will never initiate the PPrintSettingsDialog
   // protocol connection, so no need to provide an allocator here.
   NS_NOTREACHED("Allocator for PPrintSettingsDialogChild should not be "