diff -Naur sqlalchemy-migrate-0.7.2.orig/migrate/versioning/version.py sqlalchemy-migrate-0.7.2/migrate/versioning/version.py
--- sqlalchemy-migrate-0.7.2.orig/migrate/versioning/version.py	2011-10-28 15:11:43.000000000 +0000
+++ sqlalchemy-migrate-0.7.2/migrate/versioning/version.py	2012-12-20 14:33:28.035597164 +0000
@@ -27,7 +27,7 @@
 
     def __init__(self,value):
         self.value = str(int(value))
-        if self < 0:
+        if int(value) < 0:
             raise ValueError("Version number cannot be negative")
 
     def __add__(self, value):