NullpointerException when making concurrent procedure calls

I am making the same call to a store procedure multiple times with very little change in the arguments. The first call succeeds but the second call creates a null pointer exception.

The problem is caused at line 487 of MariaDbConnection class. That is when the callableStatementCache is adding a new callableStatement. That callableStatement has a the sql field populated but the value for the items that is added to the callableStatementCache has null sql field. When that value is fetched on line 479 the clone fails with a NullPointerException because the sql field cannot be null.

Below is the stack trace.
java.lang.NullPointerException
at org.mariadb.jdbc.MariaDbServerPreparedStatement.prepare(MariaDbServerPreparedStatement.java:143) at org.mariadb.jdbc.MariaDbServerPreparedStatement.clone(MariaDbServerPreparedStatement.java:134) at org.mariadb.jdbc.AbstractCallableProcedureStatement.clone(AbstractCallableProcedureStatement.java:99) at org.mariadb.jdbc.MariaDbProcedureStatement.clone(MariaDbProcedureStatement.java:119) at org.mariadb.jdbc.MariaDbProcedureStatement.clone(MariaDbProcedureStatement.java:62) at org.mariadb.jdbc.MariaDbConnection.prepareCall(MariaDbConnection.java:479) at com.zaxxer.hikari.pool.ProxyConnection.prepareCall(ProxyConnection.java:289) at com.zaxxer.hikari.pool.HikariProxyConnection.prepareCall(HikariProxyConnection.java)