--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -3,16 +3,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* container for a document and its presentation */
 
 #include "gfxContext.h"
 #include "mozilla/layout/RemotePrintJobChild.h"
+#include "mozilla/NotNull.h"
 #include "mozilla/ServoRestyleManager.h"
 #include "mozilla/ServoStyleSet.h"
 #include "nsAutoPtr.h"
 #include "nscore.h"
 #include "nsCOMPtr.h"
 #include "nsCRT.h"
 #include "nsString.h"
 #include "nsReadableUtils.h"
@@ -4217,16 +4218,31 @@ nsDocumentViewer::ExitPrintPreview()
   NS_ENSURE_TRUE(mPrintJob, NS_ERROR_FAILURE);
 
   if (GetIsPrintPreview()) {
     ReturnToGalleyPresentation();
   }
   return NS_OK;
 }
 
+NS_IMETHODIMP_(layout::RemotePrintJobChild*)
+nsDocumentViewer::GetRemotePrintJob()
+{
+  return mPrintJob ? mPrintJob->GetRemotePrintJob() : nullptr;
+}
+
+NS_IMETHODIMP_(void)
+nsDocumentViewer::SetRemotePrintJob(layout::RemotePrintJobChild* aRemotePrintJob)
+{
+  MOZ_ASSERT(aRemotePrintJob);
+  MOZ_ASSERT(mPrintJob, "Don't call this unless we're printing");
+
+  mPrintJob->SetRemotePrintJob(WrapNotNull(aRemotePrintJob));
+}
+
 //----------------------------------------------------------------------------------
 // Enumerate all the documents for their titles
 NS_IMETHODIMP
 nsDocumentViewer::EnumerateDocumentNames(uint32_t* aCount,
                                            char16_t*** aResult)
 {
 #ifdef NS_PRINTING
   NS_ENSURE_ARG(aCount);

--- a/layout/printing/nsPrintJob.h
+++ b/layout/printing/nsPrintJob.h
@@ -2,16 +2,17 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #ifndef nsPrintJob_h
 #define nsPrintJob_h
 
 #include "mozilla/Attributes.h"
+#include "mozilla/NotNull.h"
 #include "mozilla/UniquePtr.h"
 
 #include "nsCOMPtr.h"
 
 #include "nsPrintObject.h"
 #include "nsPrintData.h"
 #include "nsFrameList.h"
 #include "nsIFrame.h"
@@ -193,16 +194,27 @@ public:
     return mIsCreatingPrintPreview;
   }
 
   void SetDisallowSelectionPrint(bool aDisallowSelectionPrint)
   {
     mDisallowSelectionPrint = aDisallowSelectionPrint;
   }
 
+  RemotePrintJobChild* GetRemotePrintJob()
+  {
+    nsPrintData* data = mPrt ? mPrt : mPrtPreview;
+    return data ? data->mRemotePrintJob.get() : nullptr;
+  }
+  void SetRemotePrintJob(mozilla::NotNull<RemotePrintJobChild*> aRemotePrintJob)
+  {
+    (mPrt ? mPrt : mPrtPreview)->mRemotePrintJob = aRemotePrintJob;
+  }
+
+
 private:
   nsPrintJob& operator=(const nsPrintJob& aOther) = delete;
 
   ~nsPrintJob();
 
   nsresult CommonPrint(bool aIsPrintPreview, nsIPrintSettings* aPrintSettings,
                        nsIWebProgressListener* aWebProgressListener,
                        RemotePrintJobChild* aRemotePrintJob,

--- a/toolkit/components/browser/nsIWebBrowserPrint.idl
+++ b/toolkit/components/browser/nsIWebBrowserPrint.idl
@@ -138,16 +138,29 @@ interface nsIWebBrowserPrint : nsISuppor
 
   /**
    * Cancels the current print 
    * @return void
    */
   void cancel();
 
   /**
+   * Get our document's remote print job, if any.
+   */
+  [notxpcom] RemotePrintJobChildPtr getRemotePrintJob();
+
+  /**
+   * Set our document's remote print job.  The document viewer must already
+   * have an nsPrintJob before this is called, and the passed RemotePrintJob
+   * must not be null.  (We would crash if either of these invariantes were
+   * to be violated.)
+   */
+  [notxpcom] void setRemotePrintJob(in RemotePrintJobChildPtr aPrintJob);
+
+  /**
    * Returns an array of the names of all documents names (Title or URL)
    * and sub-documents. This will return a single item if the attr "isFramesetDocument" is false
    * and may return any number of items is "isFramesetDocument" is true
    *
    * @param  aCount - returns number of printers returned
    * @param  aResult - returns array of names
    * @return void
    */

--- a/toolkit/components/printingui/ipc/PrintDataUtils.cpp
+++ b/toolkit/components/printingui/ipc/PrintDataUtils.cpp
@@ -119,16 +119,27 @@ MockWebBrowserPrint::PrintPreviewNavigat
 }
 
 NS_IMETHODIMP
 MockWebBrowserPrint::Cancel()
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
+NS_IMETHODIMP_(layout::RemotePrintJobChild*)
+MockWebBrowserPrint::GetRemotePrintJob()
+{
+  return nullptr;
+}
+
+NS_IMETHODIMP_(void)
+MockWebBrowserPrint::SetRemotePrintJob(layout::RemotePrintJobChild* aRemotePrintJob)
+{
+}
+
 NS_IMETHODIMP
 MockWebBrowserPrint::EnumerateDocumentNames(uint32_t* aCount,
                                             char16_t*** aResult)
 {
   *aCount = 0;
   *aResult = nullptr;
 
   if (mData.printJobName().IsEmpty()) {

--- a/toolkit/components/printingui/ipc/nsPrintingProxy.cpp
+++ b/toolkit/components/printingui/ipc/nsPrintingProxy.cpp
@@ -98,16 +98,23 @@ nsPrintingProxy::ShowPrintDialog(mozIDOM
     do_GetService("@mozilla.org/gfx/printsettings-service;1", &rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
   PrintData inSettings;
   rv = printSettingsSvc->SerializeToPrintData(printSettings, webBrowserPrint,
                                               &inSettings);
   NS_ENSURE_SUCCESS(rv, rv);
 
+  // If we already have a RemotePrintJobChild then we need to reuse the same
+  // one.  (If we don't have one, one will be created for us under the
+  // SendShowPrintDialog() call below.)
+  RemotePrintJobChild* remotePrintJob = webBrowserPrint->GetRemotePrintJob();
+
+  inSettings.remotePrintJobChild() = remotePrintJob;
+
   // Now, the waiting game. The parent process should be showing
   // the printing dialog soon. In the meantime, we need to spin a
   // nested event loop while we wait for the results of the dialog
   // to be returned to us.
 
   RefPtr<PrintSettingsDialogChild> dialog = new PrintSettingsDialogChild();
   SendPPrintSettingsDialogConstructor(dialog);
 
@@ -115,16 +122,24 @@ nsPrintingProxy::ShowPrintDialog(mozIDOM
 
   SpinEventLoopUntil([&, dialog]() { return dialog->returned(); });
 
   rv = dialog->result();
   NS_ENSURE_SUCCESS(rv, rv);
 
   rv = printSettingsSvc->DeserializeToPrintSettings(dialog->data(),
                                                     printSettings);
+
+  if (!remotePrintJob) {
+    // Store the RemotePrintJobChild that was created under the
+    // SendShowPrintDialog() call so that we use the correct one in future:
+    webBrowserPrint->SetRemotePrintJob(
+      static_cast<RemotePrintJobChild*>(dialog->data().remotePrintJobChild()));
+  }
+
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsPrintingProxy::ShowProgress(mozIDOMWindowProxy*      parent,
                               nsIWebBrowserPrint*      webBrowserPrint,    // ok to be null
                               nsIPrintSettings*        printSettings,      // ok to be null
                               nsIObserver*             openDialogObserver, // ok to be null