Fix _doFakeSubmitForValidation error

diff --git i/elements/document/nuxeo-document-create.html w/elements/document/nuxeo-document-create.html
index 6b9860d0..53551ede 100644
--- i/elements/document/nuxeo-document-create.html
+++ w/elements/document/nuxeo-document-create.html
@@ -293,6 +293,8 @@ Contributors:
 
           // fake submit to trigger native validation checks and UI
           if (valid) {
+            // Hack for https://github.com/PolymerElements/iron-form/pull/185
+            this.$.form.request.method = 'get';
             this.$.form._doFakeSubmitForValidation();
           }