Index: oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/s3/AbstractS3DataStoreService.java
===================================================================
--- oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/s3/AbstractS3DataStoreService.java	(revision 1845812)
+++ oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/s3/AbstractS3DataStoreService.java	(working copy)
@@ -19,16 +19,24 @@
 
 package org.apache.jackrabbit.oak.blob.cloud.s3;
 
+import java.util.Collections;
 import java.util.Dictionary;
 import java.util.Hashtable;
 import java.util.Map;
 import java.util.Properties;
 
+import javax.jcr.RepositoryException;
+
 import org.apache.felix.scr.annotations.Component;
+import org.apache.jackrabbit.commons.SimpleValueFactory;
 import org.apache.jackrabbit.core.data.DataStore;
 import org.apache.jackrabbit.core.data.DataStoreException;
+import org.apache.jackrabbit.oak.api.Descriptors;
+import org.apache.jackrabbit.oak.osgi.OsgiWhiteboard;
 import org.apache.jackrabbit.oak.plugins.blob.AbstractSharedCachingDataStore;
 import org.apache.jackrabbit.oak.plugins.blob.datastore.AbstractDataStoreService;
+import org.apache.jackrabbit.oak.spi.descriptors.GenericDescriptors;
+import org.apache.jackrabbit.oak.spi.whiteboard.Registration;
 import org.osgi.framework.Constants;
 import org.osgi.framework.ServiceRegistration;
 import org.osgi.service.component.ComponentContext;
@@ -39,6 +47,8 @@
 
     private ServiceRegistration delegateReg;
 
+    private Registration descRegistry;
+
     @Override
     protected DataStore createDataStore(ComponentContext context, Map<String, Object> config) {
         Properties properties = new Properties();
@@ -59,11 +69,30 @@
 
         return dataStore;
     }
+    
+    @Override
+    protected void activate(ComponentContext context, Map<String, Object> config) throws RepositoryException {
+        super.activate(context, config);
+        
+        registerDescriptor(context);
+    }
 
+    private void registerDescriptor(ComponentContext context) {
+        final GenericDescriptors desc = new GenericDescriptors();
+        desc.put("store.data.binary.upload", new SimpleValueFactory().createValue(true), true, false);
+        
+        OsgiWhiteboard whiteboard = new OsgiWhiteboard(context.getBundleContext());
+        descRegistry = whiteboard.register(Descriptors.class, desc, Collections.emptyMap());
+    }
+
     protected void deactivate() throws DataStoreException {
         if (delegateReg != null) {
             delegateReg.unregister();
         }
+        if (descRegistry != null) {
+            descRegistry.unregister();
+            descRegistry = null;
+        }
         super.deactivate();
     }