Follow up to 511fce6b which missed a cast. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Igor Kozhukhov <igor@dilos.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matt Macy <mmacy@FreeBSD.org> Closes #9533
511fce6b