Incorrect "to_char" function in HSQL Dialect in Hibernate 4

Issue

We're comparing a "to_char" construct that gets a Calendar as parameter to a String. The "to_char" converts the Calendar to a String, making it possible to compare it with a String. For me it looks like Hibernate
doesn't get that "to_char" makes that conversion and only sees that there's a Calendar (within the "to_char") on the left hand side and a String parameter on the right hand side and decides (erroneously) that a comparison between the two is invalid.