OpenDataException because HBaseProtos.ServerLoad cannot be converted to an open data type

I saw this error in the master log:

Caused by: java.lang.IllegalArgumentException: Method org.apache.hadoop.hbase.master.MXBean.getRegionServers has parameter or return type that cannot be translated into an open type
at com.sun.jmx.mbeanserver.ConvertingMethod.from(ConvertingMethod.java:32)
at com.sun.jmx.mbeanserver.MXBeanIntrospector.mFrom(MXBeanIntrospector.java:63)
at com.sun.jmx.mbeanserver.MXBeanIntrospector.mFrom(MXBeanIntrospector.java:33)
at com.sun.jmx.mbeanserver.MBeanAnalyzer.initMaps(MBeanAnalyzer.java:118)
at com.sun.jmx.mbeanserver.MBeanAnalyzer.<init>(MBeanAnalyzer.java:99)
... 14 more
Caused by: javax.management.openmbean.OpenDataException: Cannot convert type: java.util.Map<java.lang.String, org.apache.hadoop.hbase.ServerLoad>
at com.sun.jmx.mbeanserver.OpenConverter.openDataException(OpenConverter.jav