diff --git a/Build.py b/Build.py
index 2e9de4a..d30607d 100755
--- a/Build.py
+++ b/Build.py
@@ -480,7 +480,10 @@ def checkCache(fnm, strip, upx):
     if upx:
         if strip:
             fnm = checkCache(fnm, 1, 0)
-        cmd = "upx --best -q \"%s\"" % cachedfile
+        bestopt = "--best"
+        if config["hasUPX"] >= (3,):
+            bestopt = "--lzma"
+        cmd = "upx " + bestopt + " -q \"%s\"" % cachedfile
     else:
         if strip:
             cmd = "strip \"%s\"" % cachedfile
diff --git a/Makespec.py b/Makespec.py
index baf8ba9..5a9e30d 100755
--- a/Makespec.py
+++ b/Makespec.py
@@ -260,7 +260,7 @@ if __name__ == '__main__':
     g.add_option("-s", "--strip", action="store_true", default=False,
                  help="strip the exe and shared libs "
                       "(don't try this on Windows)")
-    g.add_option("-X", "--upx", action="store_true", default=False,
+    g.add_option("-X", "--upx", action="store_true", default=True,
                  help="use UPX if available (works differently between "
                       "Windows and *nix)")
     #p.add_option("-Y", "--crypt", type="string", default=None, metavar="FILE",