diff --git a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/startup/RuntimeResourceDeployment.java b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/startup/RuntimeResourceDeployment.java
index e1bb21511e916..2fc5b2da24417 100644
--- a/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/startup/RuntimeResourceDeployment.java
+++ b/independent-projects/resteasy-reactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/startup/RuntimeResourceDeployment.java
@@ -563,8 +563,16 @@ private static void smartInitParameterConverter(int i, ParameterConverter quarku
     }
 
     private static boolean isNotVoid(Class<?> rawEffectiveReturnType) {
-        return rawEffectiveReturnType != Void.class
-                && rawEffectiveReturnType != void.class;
+        if (rawEffectiveReturnType == Void.class) {
+            return false;
+        }
+        if (rawEffectiveReturnType == void.class) {
+            return false;
+        }
+        if ("kotlin.Unit".equals(rawEffectiveReturnType.getName())) {
+            return false;
+        }
+        return true;
     }
 
     private void addResponseHandler(ServerResourceMethod method, List<ServerRestHandler> handlers) {