diff --git a/hacking/test-module b/hacking/test-module
index c824dcf5772..a3a6aa6fabc 100755
--- a/hacking/test-module
+++ b/hacking/test-module
@@ -64,7 +64,7 @@ def parse():
     parser.add_option('-I', '--interpreter', dest='interpreter',
         help="path to interpreter to use for this module (e.g. ansible_python_interpreter=/usr/bin/python)",
         metavar='INTERPRETER_TYPE=INTERPRETER_PATH',
-        default='python={}'.format(sys.executable))
+        default='python={0}'.format(sys.executable))
     parser.add_option('-c', '--check', dest='check', action='store_true',
         help="run the module in check mode")
     parser.add_option('-n', '--noexecute', dest='execute', action='store_false',