diff --git a/widget/gtk/nsAppShell.cpp b/widget/gtk/nsAppShell.cpp
index d56149ae9708..ed15b8201c58 100644
--- a/widget/gtk/nsAppShell.cpp
+++ b/widget/gtk/nsAppShell.cpp
@@ -169,17 +169,22 @@ nsresult nsAppShell::Init() {
     } else {
       screenManager.SetHelper(mozilla::MakeUnique<ScreenHelperGTK>());
     }
-  }
 
-  if (gtk_check_version(3, 16, 3) == nullptr) {
-    // Before 3.16.3, GDK cannot override classname by --class command line
-    // option when program uses gdk_set_program_class().
-    //
-    // See https://bugzilla.gnome.org/show_bug.cgi?id=747634
-    nsAutoString brandName;
-    mozilla::widget::WidgetUtils::GetBrandShortName(brandName);
-    if (!brandName.IsEmpty()) {
-      gdk_set_program_class(NS_ConvertUTF16toUTF8(brandName).get());
+    if (gtk_check_version(3, 16, 3) == nullptr) {
+      // Before 3.16.3, GDK cannot override classname by --class command line
+      // option when program uses gdk_set_program_class().
+      //
+      // See https://bugzilla.gnome.org/show_bug.cgi?id=747634
+      //
+      // Only bother doing this for the parent process, since it's the one
+      // creating top-level windows. (At this point, a child process hasn't
+      // received the list of registered chrome packages, so the
+      // GetBrandShortName call would fail anyway.)
+      nsAutoString brandName;
+      mozilla::widget::WidgetUtils::GetBrandShortName(brandName);
+      if (!brandName.IsEmpty()) {
+        gdk_set_program_class(NS_ConvertUTF16toUTF8(brandName).get());
+      }
     }
   }