d23b22
@@ -169,6 +169,7 @@
import java.io.File;
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.EventListener;
@@ -640,7 +641,8 @@
public class UndertowDeploymentInfoService implements Service<DeploymentInfo> {
                 JspServletBuilder.setupDeployment(d, propertyGroups, tldInfo, new UndertowJSPInstanceManager(new WebInjectionContainer(module.getClassLoader(), componentRegistryInjectedValue.getValue())));
 
                 if (mergedMetaData.getJspConfig() != null) {
-                    d.setJspConfigDescriptor(new JspConfigDescriptorImpl(tldInfo.values(), propertyGroups.values()));
+                    Collection<JspPropertyGroup> values = new HashSet<>(propertyGroups.values());
+                    d.setJspConfigDescriptor(new JspConfigDescriptorImpl(tldInfo.values(), values));
                 }
 
                 d.addServlet(jspServlet);
