diff --git a/browser/atom_browser_main_parts_mac.mm b/browser/atom_browser_main_parts_mac.mm
index 1d4a1891870e..d518c0fa70b9 100644
--- a/browser/atom_browser_main_parts_mac.mm
+++ b/browser/atom_browser_main_parts_mac.mm
@@ -23,6 +23,11 @@ void AtomBrowserMainParts::PreMainMessageLoopStart() {
   auto mainNib = [[NSNib alloc] initWithNibNamed:mainNibName bundle:base::mac::FrameworkBundle()];
   [mainNib instantiateWithOwner:application topLevelObjects:nil];
   [mainNib release];
+
+  // Prevent Cocoa from turning command-line arguments into
+  // |-application:openFiles:|, since we already handle them directly.
+  [[NSUserDefaults standardUserDefaults]
+      setObject:@"NO" forKey:@"NSTreatUnknownArgumentsAsOpen"];
 }
 
 void AtomBrowserMainParts::PostDestroyThreads() {