--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -3344,18 +3344,20 @@ ContentParent::DeallocPNeckoParent(PNeck
   delete necko;
   return true;
 }
 
 PPrintingParent*
 ContentParent::AllocPPrintingParent()
 {
 #ifdef NS_PRINTING
-  MOZ_RELEASE_ASSERT(!mPrintingParent,
-                     "Only one PrintingParent should be created per process.");
+  if (mPrintingParent) {
+    // Only one PrintingParent should be created per process.
+    return nullptr;
+  }
 
   // Create the printing singleton for this process.
   mPrintingParent = new PrintingParent();
 
   // Take another reference for IPDL code.
   mPrintingParent.get()->AddRef();
 
   return mPrintingParent.get();