diff --git a/src/saml2/pack.py b/src/saml2/pack.py
index a63d1bb..53c31cc 100644
--- a/src/saml2/pack.py
+++ b/src/saml2/pack.py
@@ -53,6 +53,7 @@ NAMESPACE = "http://schemas.xmlsoap.org/soap/envelope/"
 FORM_SPEC = """<form method="post" action="%s">
    <input type="hidden" name="%s" value="%s" />
    <input type="hidden" name="RelayState" value="%s" />
+   <input type="submit" value="Submit" />
 </form>"""