--- a/gfx/layers/Layers.cpp
+++ b/gfx/layers/Layers.cpp
@@ -2299,17 +2299,17 @@ LayerManager::Dump(std::stringstream& aS
     aStream << "<ul><li>";
   }
 #endif
   DumpSelf(aStream, aPrefix, aSorted);
 
   nsAutoCString pfx(aPrefix);
   pfx += "  ";
   if (!GetRoot()) {
-    aStream << nsPrintfCString("%s(null)", pfx.get()).get();
+    aStream << nsPrintfCString("%s(null)\n", pfx.get()).get();
     if (aDumpHtml) {
       aStream << "</li></ul>";
     }
     return;
   }
 
   if (aDumpHtml) {
     aStream << "<ul>";