diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 7786d87999be..14494f94d435 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -2934,7 +2934,9 @@ nsDocumentViewer::Print(nsIPrintSettings* aPrintSettings,
   }
 
   mPrintJob = printJob;
-  rv = printJob->Print(mDocument, aPrintSettings, aRemotePrintJob,
+
+  // Note: mDocument was null-checked earlier in this function.
+  rv = printJob->Print(*mDocument, aPrintSettings, aRemotePrintJob,
                        aWebProgressListener);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     OnDonePrinting();
@@ -2979,7 +2981,8 @@ nsDocumentViewer::PrintPreview(nsIPrintSettings* aPrintSettings,
   }
   mPrintJob = printJob;
 
-  rv = printJob->PrintPreview(doc, aPrintSettings, aWebProgressListener,
+  // Note: doc is known-non-null via NS_ENSURE_STATE null-check above.
+  rv = printJob->PrintPreview(*doc, aPrintSettings, aWebProgressListener,
                               std::move(aCallback));
   if (NS_WARN_IF(NS_FAILED(rv))) {
     OnDonePrinting();
diff --git a/layout/printing/nsPrintJob.cpp b/layout/printing/nsPrintJob.cpp
index 1d4d591cd227..58fa97110b01 100644
--- a/layout/printing/nsPrintJob.cpp
+++ b/layout/printing/nsPrintJob.cpp
@@ -196,7 +196,9 @@ void nsPrintJob::BuildNestedPrintObjects(
     }
 
     auto childPO = MakeUnique<nsPrintObject>();
-    nsresult rv = childPO->Init(docShell, doc, aParentPO.get());
+    // Note: docShell and doc are known-non-null at this point; they've been
+    // null-checked above (with null leading to 'continue' statements).
+    nsresult rv = childPO->Init(*docShell, *doc, aParentPO.get());
     if (NS_FAILED(rv)) {
       MOZ_ASSERT_UNREACHABLE("Init failed?");
     }
@@ -343,7 +345,7 @@ static void DumpLayoutData(const char* aTitleStr, const char* aURLStr,
 nsresult nsPrintJob::CommonPrint(bool aIsPrintPreview,
                                  nsIPrintSettings* aPrintSettings,
                                  nsIWebProgressListener* aWebProgressListener,
-                                 Document* aSourceDoc) {
+                                 Document& aSourceDoc) {
   // Callers must hold a strong reference to |this| to ensure that we stay
   // alive for the duration of this method, because our main owning reference
   // (on nsDocumentViewer) might be cleared during this function (if we cause
@@ -370,8 +372,8 @@ nsresult nsPrintJob::CommonPrint(bool aIsPrintPreview,
 nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
                                    nsIPrintSettings* aPrintSettings,
                                    nsIWebProgressListener* aWebProgressListener,
-                                   Document* aDoc) {
-  MOZ_ASSERT(aDoc->IsStaticDocument());
+                                   Document& aDoc) {
+  MOZ_ASSERT(aDoc.IsStaticDocument());
 
   nsresult rv;
 
@@ -411,7 +413,9 @@ nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
   {
     nsAutoScriptBlocker scriptBlocker;
     mPrintObject = MakeUnique<nsPrintObject>();
-    rv = mPrintObject->Init(docShell, aDoc);
+    // Note: docShell is implicitly non-null via do_QueryReferent necessarily
+    // having succeeded (if we got here).
+    rv = mPrintObject->Init(*docShell, aDoc);
     NS_ENSURE_SUCCESS(rv, rv);
 
     mPrintDocList.AppendElement(mPrintObject.get());
@@ -469,14 +473,14 @@ nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
 }
 
 //---------------------------------------------------------------------------------
-nsresult nsPrintJob::Print(Document* aDoc, nsIPrintSettings* aPrintSettings,
+nsresult nsPrintJob::Print(Document& aDoc, nsIPrintSettings* aPrintSettings,
                            RemotePrintJobChild* aRemotePrintJob,
                            nsIWebProgressListener* aWebProgressListener) {
   mRemotePrintJob = aRemotePrintJob;
   return CommonPrint(false, aPrintSettings, aWebProgressListener, aDoc);
 }
 
-nsresult nsPrintJob::PrintPreview(Document* aDoc,
+nsresult nsPrintJob::PrintPreview(Document& aDoc,
                                   nsIPrintSettings* aPrintSettings,
                                   nsIWebProgressListener* aWebProgressListener,
                                   PrintPreviewResolver&& aCallback) {
diff --git a/layout/printing/nsPrintJob.h b/layout/printing/nsPrintJob.h
index 37ab736e8ce2..91158be72408 100644
--- a/layout/printing/nsPrintJob.h
+++ b/layout/printing/nsPrintJob.h
@@ -99,7 +99,7 @@ class nsPrintJob final : public nsIWebProgressListener,
    * PrintPreview calls.
    */
   MOZ_CAN_RUN_SCRIPT_BOUNDARY nsresult
-  Print(Document* aSourceDoc, nsIPrintSettings* aPrintSettings,
+  Print(Document& aSourceDoc, nsIPrintSettings* aPrintSettings,
         RemotePrintJobChild* aRemotePrintJob,
         nsIWebProgressListener* aWebProgressListener);
 
@@ -114,7 +114,7 @@ class nsPrintJob final : public nsIWebProgressListener,
    * is actually our docViewer's current document!
    */
   MOZ_CAN_RUN_SCRIPT_BOUNDARY nsresult
-  PrintPreview(Document* aSourceDoc, nsIPrintSettings* aPrintSettings,
+  PrintPreview(Document& aSourceDoc, nsIPrintSettings* aPrintSettings,
                nsIWebProgressListener* aWebProgressListener,
                PrintPreviewResolver&& aCallback);
 
@@ -199,11 +199,11 @@ class nsPrintJob final : public nsIWebProgressListener,
 
   MOZ_CAN_RUN_SCRIPT nsresult CommonPrint(
       bool aIsPrintPreview, nsIPrintSettings* aPrintSettings,
-      nsIWebProgressListener* aWebProgressListener, Document* aSourceDoc);
+      nsIWebProgressListener* aWebProgressListener, Document& aSourceDoc);
 
   MOZ_CAN_RUN_SCRIPT nsresult DoCommonPrint(
       bool aIsPrintPreview, nsIPrintSettings* aPrintSettings,
-      nsIWebProgressListener* aWebProgressListener, Document* aSourceDoc);
+      nsIWebProgressListener* aWebProgressListener, Document& aSourceDoc);
 
   void FirePrintCompletionEvent();
 
diff --git a/layout/printing/nsPrintObject.cpp b/layout/printing/nsPrintObject.cpp
index aa166c75ef63..fcf5d92fc7a4 100644
--- a/layout/printing/nsPrintObject.cpp
+++ b/layout/printing/nsPrintObject.cpp
@@ -49,15 +49,12 @@ nsPrintObject::~nsPrintObject() {
 
 //------------------------------------------------------------------
 
-nsresult nsPrintObject::Init(nsIDocShell* aDocShell, Document* aDoc,
+nsresult nsPrintObject::Init(nsIDocShell& aDocShell, Document& aDoc,
                              nsPrintObject* aParent) {
-  NS_ENSURE_STATE(aDocShell);
-  NS_ENSURE_STATE(aDoc);
+  MOZ_ASSERT(aDoc.IsStaticDocument());
 
-  MOZ_ASSERT(aDoc->IsStaticDocument());
-
-  mDocShell = aDocShell;
-  mDocument = aDoc;
+  mDocShell = &aDocShell;
+  mDocument = &aDoc;
 
   if (!aParent) {
     // We are a root nsPrintObject.
@@ -66,7 +63,7 @@ nsresult nsPrintObject::Init(nsIDocShell* aDocShell, Document* aDoc,
   } else {
     // We are a nested nsPrintObject.
     mParent = aParent;
-    nsCOMPtr<nsPIDOMWindowOuter> window = aDoc->GetWindow();
+    nsCOMPtr<nsPIDOMWindowOuter> window = aDoc.GetWindow();
     mContent = window->GetFrameElementInternal();
     mFrameType = eIFrame;
   }
diff --git a/layout/printing/nsPrintObject.h b/layout/printing/nsPrintObject.h
index 26ba8f0675b4..322e3a27628e 100644
--- a/layout/printing/nsPrintObject.h
+++ b/layout/printing/nsPrintObject.h
@@ -36,7 +36,7 @@ class nsPrintObject final {
    * If aParent is nullptr (default), then this instance will be initialized as
    * a "root" nsPrintObject.  Otherwise, this will be a "nested" nsPrintObject.
    */
-  nsresult Init(nsIDocShell* aDocShell, mozilla::dom::Document* aDoc,
+  nsresult Init(nsIDocShell& aDocShell, mozilla::dom::Document& aDoc,
                 nsPrintObject* aParent = nullptr);
 
   void DestroyPresentation();