This fragment:

GlobalConfiguration gc = GlobalConfiguration.getClusteredDefault();
Configuration config = new Configuration();
config.setCacheMode(Configuration.CacheMode.DIST_SYNC);
config.setNumOwners(1); // no redundancy

CacheManager cacheManager = new DefaultCacheManager(gc, config);
Cache cache = cacheManager.getCache();

cache.put("key", "value");

cache.clear();
assert cache.isEmpty();

raises a NullPointerException at cache.clear() invokation.
It works correctly both using other cache modes (LOCAL, REPL and INVALIDATION) or avoiding to set config.setNumOwners to 1.

The stacktrace is:

java.lang.NullPointerException
at org.infinispan.interceptors.DistributionInterceptor.isSingleOwnerAndLocal(DistributionInterceptor.java:317)
at org.infinispan.interceptors.DistributionInterceptor.handleWriteCommand(DistributionInterceptor.java:276)
at org.infinispan.interceptors.DistributionInterceptor.visitClearCommand(DistributionInterceptor.java:180)
at org.infinispan.commands.write.ClearCommand.acceptVisitor(ClearCommand.java:58)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.LockingInterceptor.visitClearCommand(LockingInterceptor.java:169)
at org.infinispan.commands.write.ClearCommand.acceptVisitor(ClearCommand.java:58)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.base.CommandInterceptor.handleDefault(CommandInterceptor.java:132)
....