Titan storage.backend=inmemory Causes Incompatible Data Type Exception

I've been using titan-cassandra storage.backend=cassandra in my testing environment and recently learned that I can simply plop in storage.backend=inmemory to test with an in-memory graph. As this will drastically increase the speed of the hundreds of tests - this sounds great. But, making this change to my otherwise simple test configuration causes many of my once passing tests to fail. Here's my configuration:

storage.backend=inmemory
storage.hostname=localhost
storage.cassandra.keyspace=test

There are two errors that come up, the vast majority being:

java.lang.IllegalArgumentException: Incompatible data types for: variable

while much less commonly:

com.thinkaurelius.titan.core.TitanException: Could not commit transaction due to exception during persistence

Any idea on how I can resolve these issues?