diff --git a/pycam/Utils/__init__.py b/pycam/Utils/__init__.py
index 83d26eb2..b026567f 100644
--- a/pycam/Utils/__init__.py
+++ b/pycam/Utils/__init__.py
@@ -30,6 +30,8 @@
 # import win32com
 # import win32api
 
+if sys.version_info.major < 3:
+    raise RuntimeError("Only work with Python 3 or later")
 
 # setproctitle is (optionally) imported
 try:
diff --git a/setup.py b/setup.py
index e61cfaa0..6eed38c2 100755
--- a/setup.py
+++ b/setup.py
@@ -37,6 +37,7 @@
     author_email="devel@sumpfralle.de",
     provides=["pycam"],
     requires=["PyOpenGL", "PyYAML"],
+    python_requires='>=3.0',
     url="http://pycam.sourceforge.net/",
     download_url="http://sourceforge.net/projects/pycam/files",
     keywords=["3-axis", "cnc", "cam", "toolpath", "machining", "g-code"],