diff --git a/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/resource/basic/ResourceLocatorTest.java b/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/resource/basic/ResourceLocatorTest.java
index 7c60b603e53d7..020a3458cb1d3 100644
--- a/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/resource/basic/ResourceLocatorTest.java
+++ b/extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment/src/test/java/io/quarkus/resteasy/reactive/server/test/resource/basic/ResourceLocatorTest.java
@@ -134,8 +134,7 @@ public void testAnnotationFreeSubresource() throws Exception {
             Assertions.assertEquals(Response.Status.OK.getStatusCode(), response.getStatus());
             Assertions.assertEquals(response.readEntity(String.class), "got");
             Assertions.assertNotNull(response.getHeaderString("Content-Type"));
-            Assertions.assertNotNull(response.getHeaderString("Content-Type"));
-            Assertions.assertEquals(MediaType.TEXT_PLAIN_TYPE.toString(),
+            Assertions.assertEquals("text/plain;charset=UTF-8",
                     response.getHeaderString("Content-Type"));
         }
         {
diff --git a/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/EndpointIndexer.java b/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/EndpointIndexer.java
index c09283af77e5b..74d30f8121baa 100644
--- a/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/EndpointIndexer.java
+++ b/independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/EndpointIndexer.java
@@ -54,6 +54,7 @@
 import java.lang.reflect.Modifier;
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.nio.charset.StandardCharsets;
 import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -490,6 +491,7 @@ private ResourceMethod createResourceMethod(ClassInfo currentClassInfo, ClassInf
 
             String[] produces = extractProducesConsumesValues(currentMethodInfo.annotation(PRODUCES), classProduces);
             produces = applyDefaultProduces(produces, nonAsyncReturnType);
+            produces = addDefaultCharsets(produces);
 
             String sseElementType = classSseElementType;
             AnnotationInstance sseElementTypeAnnotation = currentMethodInfo.annotation(REST_SSE_ELEMENT_TYPE);
@@ -626,6 +628,22 @@ private String[] applyDefaultProduces(String[] produces, Type nonAsyncReturnType
         return applyAdditionalDefaults(nonAsyncReturnType);
     }
 
+    // see https://github.com/quarkusio/quarkus/issues/19535
+    private String[] addDefaultCharsets(String[] produces) {
+        if ((produces == null) || (produces.length == 0)) {
+            return produces;
+        }
+        List<String> result = new ArrayList<>(produces.length);
+        for (String p : produces) {
+            if (p.equals(MediaType.TEXT_PLAIN)) {
+                result.add(MediaType.TEXT_PLAIN + ";charset=" + StandardCharsets.UTF_8.name());
+            } else {
+                result.add(p);
+            }
+        }
+        return result.toArray(EMPTY_STRING_ARRAY);
+    }
+
     protected String[] applyAdditionalDefaults(Type nonAsyncReturnType) {
         // FIXME: primitives
         if (STRING.equals(nonAsyncReturnType.name()))
@@ -724,7 +742,7 @@ private static String[] extractProducesConsumesValues(AnnotationInstance annotat
                     result.add(t.trim());
                 }
             }
-            return result.toArray(new String[0]);
+            return result.toArray(EMPTY_STRING_ARRAY);
         } else {
             return originalStrings;
         }