diff --git a/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/handlers/ClientSetResponseEntityRestHandler.java b/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/handlers/ClientSetResponseEntityRestHandler.java
index 8b3236f4951e2..cb811043af91b 100644
--- a/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/handlers/ClientSetResponseEntityRestHandler.java
+++ b/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/handlers/ClientSetResponseEntityRestHandler.java
@@ -5,7 +5,6 @@
 
 import jakarta.ws.rs.client.Entity;
 import jakarta.ws.rs.core.MediaType;
-import jakarta.ws.rs.core.MultivaluedMap;
 import jakarta.ws.rs.core.Response;
 import jakarta.ws.rs.core.Response.StatusType;
 
@@ -17,6 +16,7 @@
 import org.jboss.resteasy.reactive.client.spi.ClientRestHandler;
 import org.jboss.resteasy.reactive.common.core.Serialisers;
 import org.jboss.resteasy.reactive.common.jaxrs.StatusTypeImpl;
+import org.jboss.resteasy.reactive.common.util.QuarkusMultivaluedHashMap;
 
 import io.vertx.core.buffer.Buffer;
 
@@ -88,7 +88,7 @@ private ByteArrayInputStream entityStreamOfAbortedResponseOf(RestClientRequestCo
             entity = Entity.entity(untypedEntity, mediaType);
         }
         // FIXME: pass headers?
-        Buffer buffer = context.writeEntity(entity, (MultivaluedMap) Serialisers.EMPTY_MULTI_MAP,
+        Buffer buffer = context.writeEntity(entity, new QuarkusMultivaluedHashMap<>(),
                 Serialisers.NO_WRITER_INTERCEPTOR);
         return new ByteArrayInputStream(buffer.getBytes());
     }
diff --git a/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/impl/InboundSseEventImpl.java b/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/impl/InboundSseEventImpl.java
index 80c90ee0c0446..66cecfadab348 100644
--- a/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/impl/InboundSseEventImpl.java
+++ b/independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/impl/InboundSseEventImpl.java
@@ -14,6 +14,7 @@
 
 import org.jboss.resteasy.reactive.common.core.Serialisers;
 import org.jboss.resteasy.reactive.common.jaxrs.ConfigurationImpl;
+import org.jboss.resteasy.reactive.common.util.QuarkusMultivaluedHashMap;
 
 public class InboundSseEventImpl implements InboundSseEvent {
 
@@ -120,7 +121,7 @@ public <T> T readData(GenericType<T> type, MediaType mediaType) {
         InputStream in = new ByteArrayInputStream(data.getBytes(StandardCharsets.UTF_8));
         try {
             return (T) ClientSerialisers.invokeClientReader(null, type.getRawType(), type.getType(),
-                    mediaType, null, null, Serialisers.EMPTY_MULTI_MAP,
+                    mediaType, null, null, new QuarkusMultivaluedHashMap<>(),
                     serialisers, in, Serialisers.NO_READER_INTERCEPTOR, configuration);
         } catch (IOException e) {
             throw new UncheckedIOException(e);
diff --git a/independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/common/core/Serialisers.java b/independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/common/core/Serialisers.java
index b214cc5691aab..18cbc955d960f 100644
--- a/independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/common/core/Serialisers.java
+++ b/independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/common/core/Serialisers.java
@@ -14,7 +14,6 @@
 
 import jakarta.ws.rs.RuntimeType;
 import jakarta.ws.rs.core.MediaType;
-import jakarta.ws.rs.core.MultivaluedMap;
 import jakarta.ws.rs.core.Response;
 import jakarta.ws.rs.ext.MessageBodyReader;
 import jakarta.ws.rs.ext.MessageBodyWriter;
@@ -32,7 +31,6 @@
 public abstract class Serialisers {
     public static final Annotation[] NO_ANNOTATION = new Annotation[0];
     public static final ReaderInterceptor[] NO_READER_INTERCEPTOR = new ReaderInterceptor[0];
-    public static final MultivaluedMap<String, Object> EMPTY_MULTI_MAP = new QuarkusMultivaluedHashMap<>();
     public static final WriterInterceptor[] NO_WRITER_INTERCEPTOR = new WriterInterceptor[0];
     protected static final Map<Class<?>, Class<?>> primitivesToWrappers = new HashMap<>();
     // FIXME: spec says we should use generic type, but not sure how to pass that type from Jandex to reflection
diff --git a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java
index da88aa6560dd5..f0a3824f25c42 100644
--- a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java
+++ b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java
@@ -18,6 +18,7 @@
 
 import org.jboss.resteasy.reactive.common.core.Serialisers;
 import org.jboss.resteasy.reactive.common.util.CommonSseUtil;
+import org.jboss.resteasy.reactive.common.util.QuarkusMultivaluedHashMap;
 import org.jboss.resteasy.reactive.server.handlers.PublisherResponseHandler;
 import org.jboss.resteasy.reactive.server.jaxrs.OutboundSseEventImpl;
 import org.jboss.resteasy.reactive.server.spi.ServerHttpResponse;
@@ -138,7 +139,7 @@ private static String serialiseDataToString(ResteasyReactiveRequestContext conte
             if (writer.isWriteable(entityClass, entityType, Serialisers.NO_ANNOTATION, mediaType)) {
                 // FIXME: spec doesn't really say what headers we should use here
                 writer.writeTo(entity, entityClass, entityType, Serialisers.NO_ANNOTATION, mediaType,
-                        Serialisers.EMPTY_MULTI_MAP, baos);
+                        new QuarkusMultivaluedHashMap<>(), baos);
                 wrote = true;
                 break;
             }
diff --git a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/StreamingUtil.java b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/StreamingUtil.java
index ab04df5cff81c..0903202a53402 100644
--- a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/StreamingUtil.java
+++ b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/StreamingUtil.java
@@ -14,6 +14,7 @@
 import jakarta.ws.rs.ext.MessageBodyWriter;
 
 import org.jboss.resteasy.reactive.common.core.Serialisers;
+import org.jboss.resteasy.reactive.common.util.QuarkusMultivaluedHashMap;
 import org.jboss.resteasy.reactive.server.StreamingOutputStream;
 import org.jboss.resteasy.reactive.server.handlers.PublisherResponseHandler;
 import org.jboss.resteasy.reactive.server.spi.ServerHttpResponse;
@@ -66,7 +67,7 @@ private static byte[] serialiseEntity(ResteasyReactiveRequestContext context, Ob
             if (writer.isWriteable(entityClass, entityType, Serialisers.NO_ANNOTATION, mediaType)) {
                 // FIXME: spec doesn't really say what headers we should use here
                 writer.writeTo(entity, entityClass, entityType, Serialisers.NO_ANNOTATION, mediaType,
-                        Serialisers.EMPTY_MULTI_MAP, baos);
+                        new QuarkusMultivaluedHashMap<>(), baos);
                 wrote = true;
                 break;
             }
diff --git a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/multipart/MultipartMessageBodyWriter.java b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/multipart/MultipartMessageBodyWriter.java
index a8ff157a4af84..6896e96e67225 100644
--- a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/multipart/MultipartMessageBodyWriter.java
+++ b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/multipart/MultipartMessageBodyWriter.java
@@ -24,6 +24,7 @@
 
 import org.jboss.resteasy.reactive.common.core.Serialisers;
 import org.jboss.resteasy.reactive.common.reflection.ReflectionBeanFactoryCreator;
+import org.jboss.resteasy.reactive.common.util.QuarkusMultivaluedHashMap;
 import org.jboss.resteasy.reactive.multipart.FileDownload;
 import org.jboss.resteasy.reactive.server.NoopCloseAndFlushOutputStream;
 import org.jboss.resteasy.reactive.server.core.CurrentRequestManager;
@@ -192,7 +193,7 @@ private void writeEntity(OutputStream os, Object entity, MediaType mediaType, Re
                 try (NoopCloseAndFlushOutputStream writerOutput = new NoopCloseAndFlushOutputStream(os)) {
                     // FIXME: spec doesn't really say what headers we should use here
                     writer.writeTo(entity, entityClass, entityType, Serialisers.NO_ANNOTATION, mediaType,
-                            Serialisers.EMPTY_MULTI_MAP, writerOutput);
+                            new QuarkusMultivaluedHashMap<>(), writerOutput);
                     wrote = true;
                 }