diff --git a/u2flib_server/__init__.py b/u2flib_server/__init__.py
index <HASH>..<HASH> 100644
--- a/u2flib_server/__init__.py
+++ b/u2flib_server/__init__.py
@@ -25,4 +25,4 @@
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
-__version__ = "3.3.0-dev"
+__version__ = "4.0.0-dev"
Increment version to <I>