diff --git a/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ClassicOidcClientRequestFilterDelegate.java b/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ClassicOidcClientRequestFilterDelegate.java
index 677ee5b4..ecae242d 100644
--- a/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ClassicOidcClientRequestFilterDelegate.java
+++ b/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ClassicOidcClientRequestFilterDelegate.java
@@ -1,6 +1,7 @@
 package io.quarkiverse.openapi.generator.oidc;
 
 import java.io.IOException;
+import java.util.Collections;
 
 import jakarta.annotation.Priority;
 import jakarta.enterprise.inject.spi.InjectionPoint;
@@ -42,7 +43,7 @@ protected java.util.Optional<String> clientId() {
     public void filter(ClientRequestContext requestContext) throws IOException {
         try {
             String accessToken = this.getAccessToken();
-            requestContext.getHeaders().add(HttpHeaders.AUTHORIZATION, "Bearer " + accessToken);
+            requestContext.getHeaders().put(HttpHeaders.AUTHORIZATION, Collections.singletonList("Bearer " + accessToken));
         } catch (DisabledOidcClientException ex) {
             LOG.debug("Client is disabled, acquiring and propagating the token is not necessary");
         } catch (RuntimeException ex) {
diff --git a/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ReactiveOidcClientRequestFilterDelegate.java b/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ReactiveOidcClientRequestFilterDelegate.java
index cdbd5796..2cd359c3 100644
--- a/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ReactiveOidcClientRequestFilterDelegate.java
+++ b/client/oidc/src/main/java/io/quarkiverse/openapi/generator/oidc/ReactiveOidcClientRequestFilterDelegate.java
@@ -1,6 +1,7 @@
 package io.quarkiverse.openapi.generator.oidc;
 
 import java.io.IOException;
+import java.util.Collections;
 
 import jakarta.annotation.Priority;
 import jakarta.enterprise.inject.spi.InjectionPoint;
@@ -57,8 +58,8 @@ public void filter(ResteasyReactiveClientRequestContext requestContext) {
         requestContext.suspend();
 
         super.getTokens().subscribe().with(tokens -> {
-            requestContext.getHeaders().putSingle(HttpHeaders.AUTHORIZATION,
-                    BEARER_SCHEME_WITH_SPACE + tokens.getAccessToken());
+            requestContext.getHeaders().put(HttpHeaders.AUTHORIZATION,
+                    Collections.singletonList(BEARER_SCHEME_WITH_SPACE + tokens.getAccessToken()));
             requestContext.resume();
         }, t -> {
             if (t instanceof DisabledOidcClientException) {
diff --git a/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/OAuth2AuthenticationProviderTest.java b/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/OAuth2AuthenticationProviderTest.java
index aa54b54b..5c118378 100644
--- a/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/OAuth2AuthenticationProviderTest.java
+++ b/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/OAuth2AuthenticationProviderTest.java
@@ -4,6 +4,7 @@
 import static org.mockito.Mockito.when;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Stream;
@@ -57,6 +58,7 @@ public class OAuth2AuthenticationProviderTest {
     @BeforeEach
     void setUp() {
         headers = new MultivaluedHashMap<>();
+        headers.put(HttpHeaders.AUTHORIZATION, Collections.singletonList("TEST"));
         Mockito.lenient().doReturn(headers).when(requestContext).getHeaders();
 
         classicDelegate = Mockito.mock(ClassicOidcClientRequestFilterDelegate.class);
diff --git a/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/ReactiveOAuth2AuthenticationProviderTest.java b/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/ReactiveOAuth2AuthenticationProviderTest.java
index a450f3cb..9e81dc9b 100644
--- a/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/ReactiveOAuth2AuthenticationProviderTest.java
+++ b/client/oidc/src/test/java/io/quarkiverse/openapi/generator/oidc/ReactiveOAuth2AuthenticationProviderTest.java
@@ -4,6 +4,7 @@
 import static org.mockito.Mockito.when;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Stream;
@@ -61,6 +62,7 @@ public class ReactiveOAuth2AuthenticationProviderTest {
     @BeforeEach
     void setUp() {
         headers = new MultivaluedHashMap<>();
+        headers.put(HttpHeaders.AUTHORIZATION, Collections.singletonList("TEST"));
         Mockito.lenient().doReturn(headers).when(reactiveRequestContext).getHeaders();
         Mockito.lenient().doReturn(restClientRequestContext).when(reactiveRequestContext).getRestClientRequestContext();
         Mockito.lenient().doAnswer(invocationOnMock -> restClientRequestContext.setSuspended(true))