diff --git a/discovery/src/main/java/org/wildfly/extension/discovery/AggregateDiscoveryProviderRegistrar.java b/discovery/src/main/java/org/wildfly/extension/discovery/AggregateDiscoveryProviderRegistrar.java
index 68de5fff9cb..51c2ee66135 100644
--- a/discovery/src/main/java/org/wildfly/extension/discovery/AggregateDiscoveryProviderRegistrar.java
+++ b/discovery/src/main/java/org/wildfly/extension/discovery/AggregateDiscoveryProviderRegistrar.java
@@ -4,7 +4,6 @@
  */
 package org.wildfly.extension.discovery;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.function.Supplier;
@@ -13,13 +12,12 @@
 import org.jboss.as.controller.OperationContext;
 import org.jboss.as.controller.OperationFailedException;
 import org.jboss.as.controller.PathElement;
-import org.jboss.as.controller.StringListAttributeDefinition;
-import org.jboss.as.controller.registry.AttributeAccess.Flag;
 import org.jboss.dmr.ModelNode;
 import org.wildfly.discovery.impl.AggregateDiscoveryProvider;
 import org.wildfly.discovery.spi.DiscoveryProvider;
 import org.wildfly.subsystem.resource.ResourceDescriptor;
 import org.wildfly.subsystem.resource.capability.CapabilityReference;
+import org.wildfly.subsystem.resource.capability.CapabilityReferenceListAttributeDefinition;
 import org.wildfly.subsystem.service.ResourceServiceInstaller;
 import org.wildfly.subsystem.service.ServiceDependency;
 import org.wildfly.subsystem.service.capability.CapabilityServiceInstaller;
@@ -32,10 +30,7 @@ public class AggregateDiscoveryProviderRegistrar extends DiscoveryProviderRegist
 
     static final PathElement PATH = PathElement.pathElement("aggregate-provider");
 
-    private static final StringListAttributeDefinition PROVIDER_NAMES = new StringListAttributeDefinition.Builder("providers")
-            .setCapabilityReference(CapabilityReference.builder(DISCOVERY_PROVIDER_CAPABILITY, DISCOVERY_PROVIDER_DESCRIPTOR).build())
-            .setFlags(Flag.RESTART_RESOURCE_SERVICES)
-            .build();
+    private static final CapabilityReferenceListAttributeDefinition<DiscoveryProvider> PROVIDER_NAMES = new CapabilityReferenceListAttributeDefinition.Builder<>("providers", CapabilityReference.builder(DISCOVERY_PROVIDER_CAPABILITY, DISCOVERY_PROVIDER_DESCRIPTOR).build()).build();
 
     static final Collection<AttributeDefinition> ATTRIBUTES = List.of(PROVIDER_NAMES);
 
@@ -45,19 +40,15 @@ public class AggregateDiscoveryProviderRegistrar extends DiscoveryProviderRegist
 
     @Override
     public ResourceServiceInstaller configure(OperationContext context, ModelNode model) throws OperationFailedException {
-        List<String> providers = PROVIDER_NAMES.unwrap(context, model);
-        List<ServiceDependency<DiscoveryProvider>> dependencies = new ArrayList<>(providers.size());
-        for (String provider : providers) {
-            dependencies.add(ServiceDependency.on(DISCOVERY_PROVIDER_DESCRIPTOR, provider));
-        }
+        List<ServiceDependency<DiscoveryProvider>> providers = PROVIDER_NAMES.resolve(context, model);
         Supplier<DiscoveryProvider> factory = new Supplier<>() {
             @Override
             public DiscoveryProvider get() {
-                return new AggregateDiscoveryProvider(dependencies.stream().map(Supplier::get).toArray(DiscoveryProvider[]::new));
+                return new AggregateDiscoveryProvider(providers.stream().map(Supplier::get).toArray(DiscoveryProvider[]::new));
             }
         };
         return CapabilityServiceInstaller.builder(DISCOVERY_PROVIDER_CAPABILITY, factory)
-                .requires(dependencies)
+                .requires(providers)
                 .build();
     }
 }
diff --git a/io/subsystem/src/main/java/org/wildfly/extension/io/IOSubsystemRegistrar.java b/io/subsystem/src/main/java/org/wildfly/extension/io/IOSubsystemRegistrar.java
index 7942677c8a0..a041bea3e5b 100644
--- a/io/subsystem/src/main/java/org/wildfly/extension/io/IOSubsystemRegistrar.java
+++ b/io/subsystem/src/main/java/org/wildfly/extension/io/IOSubsystemRegistrar.java
@@ -9,21 +9,17 @@
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import org.jboss.as.controller.AttributeDefinition;
 import org.jboss.as.controller.OperationContext;
 import org.jboss.as.controller.OperationFailedException;
 import org.jboss.as.controller.PathElement;
 import org.jboss.as.controller.ResourceDefinition;
 import org.jboss.as.controller.ResourceRegistration;
-import org.jboss.as.controller.SimpleAttributeDefinitionBuilder;
 import org.jboss.as.controller.SubsystemRegistration;
 import org.jboss.as.controller.capability.RuntimeCapability;
 import org.jboss.as.controller.descriptions.ParentResourceDescriptionResolver;
 import org.jboss.as.controller.descriptions.SubsystemResourceDescriptionResolver;
-import org.jboss.as.controller.registry.AttributeAccess;
 import org.jboss.as.controller.registry.ManagementResourceRegistration;
 import org.jboss.dmr.ModelNode;
-import org.jboss.dmr.ModelType;
 import org.wildfly.common.function.Functions;
 import org.wildfly.io.IOServiceDescriptor;
 import org.wildfly.subsystem.resource.ManagementResourceRegistrar;
@@ -31,11 +27,13 @@
 import org.wildfly.subsystem.resource.ResourceDescriptor;
 import org.wildfly.subsystem.resource.SubsystemResourceDefinitionRegistrar;
 import org.wildfly.subsystem.resource.capability.CapabilityReference;
+import org.wildfly.subsystem.resource.capability.CapabilityReferenceAttributeDefinition;
 import org.wildfly.subsystem.resource.operation.ResourceOperationRuntimeHandler;
 import org.wildfly.subsystem.service.ResourceServiceConfigurator;
 import org.wildfly.subsystem.service.ResourceServiceInstaller;
 import org.wildfly.subsystem.service.ServiceDependency;
 import org.wildfly.subsystem.service.capability.CapabilityServiceInstaller;
+import org.xnio.XnioWorker;
 
 /**
  * @author <a href="mailto:tomaz.cerar@redhat.com">Tomaz Cerar</a> (c) 2013 Red Hat Inc.
@@ -52,10 +50,8 @@ class IOSubsystemRegistrar implements SubsystemResourceDefinitionRegistrar, Reso
 
     static final ModelNode LEGACY_DEFAULT_WORKER = new ModelNode("default");
 
-    static final AttributeDefinition DEFAULT_WORKER = new SimpleAttributeDefinitionBuilder("default-worker", ModelType.STRING)
+    static final CapabilityReferenceAttributeDefinition<XnioWorker> DEFAULT_WORKER = new CapabilityReferenceAttributeDefinition.Builder<>("default-worker", CapabilityReference.builder(DEFAULT_WORKER_CAPABILITY, IOServiceDescriptor.WORKER).build())
             .setRequired(false)
-            .setCapabilityReference(CapabilityReference.builder(DEFAULT_WORKER_CAPABILITY, IOServiceDescriptor.WORKER).build())
-            .setFlags(AttributeAccess.Flag.RESTART_RESOURCE_SERVICES)
             .build();
 
     // Tracks max-threads for all workers