diff --git a/tools/xm-test/lib/XmTestLib/Test.py b/tools/xm-test/lib/XmTestLib/Test.py
index 32d1574eae..ee49ccd358 100644
--- a/tools/xm-test/lib/XmTestLib/Test.py
+++ b/tools/xm-test/lib/XmTestLib/Test.py
@@ -131,12 +131,12 @@ def becomeNonRoot():
         if os.geteuid() == 0:
             FAIL("Could not become a non-root user")
 
-def FAIL(reason):
-    print "\nREASON: %s" % reason
+def FAIL(format, *args):
+    print "\nREASON:", (format % args)
     sys.exit(TEST_FAIL)
 
-def SKIP(reason):
-    print "\nREASON: %s" % reason
+def SKIP(format, *args):
+    print "\nREASON:", (format % args)
     sys.exit(TEST_SKIP)
 
 def saveLog(logText, filename=None):