java.locale.providers set to HOST causes Log4j2 to crash in Java 9

When using the JUL log manager, setting the java.locale.providers property to "HOST" causes log4j2 to crash when you next log something.

import java.util.logging.Level;
import java.util.logging.Logger;

public class LocalePropertyTest {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        System.setProperty("java.locale.providers", "HOST,JRE,SPI");
        System.setProperty("java.util.logging.manager", "org.apache.logging.log4j.jul.LogManager");
        Logger.getLogger(LocalePropertyTest.class.getName()).log(Level.WARNING, "this is a test");
    }
}

Used the following libraries:

log4j-jul-2.9.1.jar
log4j-core-2.9.1.jar
log4j-api-2.9.1.jar

The error is very long. Here are the first few lines:

ERROR StatusLogger Error creating converter for d
java.lang.reflect.InvocationTargetException
at jdk.internal.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.apache.logging.log4j.core.pattern.PatternParser.createConverter(PatternParser.java:582)
at org.apache.logging.log4j.core.pattern.PatternParser.finalizeConverter(PatternParser.java:638)
at org.apache.logging.log4j.core.pattern.PatternParser.parse(PatternParser.java:414)
at org.apache.logging.log4j.core.pattern.PatternParser.parse(PatternParser.java:177)
at org.apache.logging.log4j.core.layout.PatternLayout$SerializerBuilder.build(PatternLayout.java:376)