diff --git a/AppKit/CPWindow/CPWindow.j b/AppKit/CPWindow/CPWindow.j
index 01bf60f10..c1e14a813 100644
--- a/AppKit/CPWindow/CPWindow.j
+++ b/AppKit/CPWindow/CPWindow.j
@@ -1856,7 +1856,9 @@ CPTexturedBackgroundWindowMask
 */
 - (BOOL)canBecomeKeyWindow
 {
-    return YES;
+    // In Cocoa only resizable or titled windows return YES here by default. But the main browser window in Cappuccino
+    // doesn't have these masks even that it's both titled and resizable, so we return YES when isFullPlatformWindow too.
+    return (_styleMask & CPResizableWindowMask) || (_styleMask & CPResizableWindowMask) || [self isFullPlatformWindow];
 }
 
 /*!