While trying to run the redmine test suite, I observed the following behaviour. While all migrations work and all test pass successfully, the creation of db/schema.rb was faulty. While MRI produced the following line: t.text "text", :limit => 2147483647 JRuby ommited the limit parameter t.text "text" resulting in a much to small column width in the test database. http://github.com/finnlabs/activerecord-jdbc-adapter/commit/bfd62eaf6349ec586dd0b82fffdac6864b6d76ff exposes this behaviour in a test case for AR-JDBC. It passes on MRI but fails on the current master of AR-JDBC http://github.com/finnlabs/activerecord-jdbc-adapter/commit/1e0b4e8f431f555c6de762d933738c9c21cf75f8 contains a proposed fix. I am sure, there might be better implementation strategies, but this one worked for me. With the help of http://github.com/finnlabs/activerecord-jdbc-adapter/commit/9461fd7f8844e5c55286be59920a85fda0926b1a I made the MySQL test run on MRI. They seem to be broken ATM. I have also added the patch files, for your convenience.