diff --git a/flye/__build__.py b/flye/__build__.py
index d9eb4a2b..a191ffb7 100644
--- a/flye/__build__.py
+++ b/flye/__build__.py
@@ -1 +1 @@
-__build__ = 1799
+__build__ = 1800
diff --git a/flye/main.py b/flye/main.py
index f4a00c8b..e3896c51 100644
--- a/flye/main.py
+++ b/flye/main.py
@@ -35,6 +35,9 @@
 from flye.repeat_graph.repeat_graph import RepeatGraph
 from flye.six.moves import range
 
+if sys.version_info[0] == 2:
+    raise Exception("Python 2 is unsupported")
+
 logger = logging.getLogger()
 
 class ResumeException(Exception):