diff --git a/Library/Formula/qemu.rb b/Library/Formula/qemu.rb
index 7039ed8700..c65c415e39 100644
--- a/Library/Formula/qemu.rb
+++ b/Library/Formula/qemu.rb
@@ -16,7 +16,12 @@ class Qemu < Formula
   depends_on "glib"
   depends_on "pixman"
   depends_on "vde" => :optional
-  depends_on "sdl" => :optional
+  if MacOS.version < :leopard
+    # Enable the SDL UI by default on OS X versions older than 10.5 because the Cocoa UI (which is otherwise enabled by default) is unavailable on these OS X versions.
+    depends_on "sdl" => :recommended
+  else
+    depends_on "sdl" => :optional
+  end
   depends_on "gtk+" => :optional
   depends_on "libssh2" => :optional
 
@@ -46,7 +51,7 @@ def install
       --disable-guest-agent
     ]
 
-    # Cocoa UI uses features that require 10.5 or newer
+    # The Cocoa UI uses features that require OS X 10.5 or newer, so we only enable it by default on those OS X versions.
     if MacOS.version > :tiger
       args << "--enable-cocoa"
     else