AWS Data Pipeline RedshiftCopy activity cannot find suitable drivers

I've set up a RedshiftCopy activity in AWS Data Pipeline, but it keeps failing with the following error:

java.lang.RuntimeException: java.sql.SQLException: No suitable driver found for <REDACTED> at private.com.google.common.base.Throwables.propagate(Unknown Source) at amazonaws.datapipeline.database.ConnectionFactory.getConnection(ConnectionFactory.java:145) at amazonaws.datapipeline.database.ConnectionFactory.getRedshiftDatabaseConnection(ConnectionFactory.java:80) at amazonaws.datapipeline.database.ConnectionFactory.getConnection(ConnectionFactory.java:47) at amazonaws.datapipeline.database.ConnectionFactory.getConnectionWithCredentials(ConnectionFactory.java:230) at amazonaws.datapipeline.redshift.RedshiftActivityRunnerFactory$RedshiftActivityRunner.<init>(RedshiftActivityRunnerFactory.java:29) at amazonaws.datapipeline.redshift.RedshiftActivityRunnerFactory.create(RedshiftActivityRunnerFactory.java:48) at amazonaws.datapipeline.activity.RedshiftCopyActivity.runActivity(RedshiftCopyActivity.java:49) at amazona ..etc

The "runsOn" EC2 instance is a Data Pipeline-managed resource, so I'm confused by the error, because I assumed that any instance that gets spun up by Data Pipeline, will have all the necessary resources installed.

Has anyone encountered this error before? What, if anything, did you do to fix it?

Thanks in advance.