diff --git a/experimental/fluent/func/src/main/java/io/serverlessworkflow/fluent/func/FuncSetTaskBuilder.java b/experimental/fluent/func/src/main/java/io/serverlessworkflow/fluent/func/FuncSetTaskBuilder.java
index 304a67c81..d8c3d0f0f 100644
--- a/experimental/fluent/func/src/main/java/io/serverlessworkflow/fluent/func/FuncSetTaskBuilder.java
+++ b/experimental/fluent/func/src/main/java/io/serverlessworkflow/fluent/func/FuncSetTaskBuilder.java
@@ -15,8 +15,6 @@
  */
 package io.serverlessworkflow.fluent.func;
 
-import io.serverlessworkflow.api.types.Set;
-import io.serverlessworkflow.api.types.SetTask;
 import io.serverlessworkflow.api.types.func.MapSetTaskConfiguration;
 import io.serverlessworkflow.fluent.func.spi.ConditionalTaskBuilder;
 import io.serverlessworkflow.fluent.spec.SetTaskBuilder;
@@ -25,23 +23,8 @@
 public class FuncSetTaskBuilder extends SetTaskBuilder
     implements ConditionalTaskBuilder<FuncSetTaskBuilder> {
 
-  private final SetTask task;
-
-  FuncSetTaskBuilder() {
-    this.task = new SetTask();
-    this.setTask(task);
-  }
-
   public FuncSetTaskBuilder expr(Map<String, Object> map) {
-    if (this.task.getSet() == null) {
-      this.task.setSet(new Set());
-    }
-    this.task.getSet().withSetTaskConfiguration(new MapSetTaskConfiguration(map));
+    this.setTaskConfiguration = new MapSetTaskConfiguration(map);
     return this;
   }
-
-  @Override
-  public SetTask build() {
-    return this.task;
-  }
 }
diff --git a/experimental/lambda/src/test/java/io/serverless/workflow/impl/executors/func/FluentDSLCallTest.java b/experimental/lambda/src/test/java/io/serverless/workflow/impl/executors/func/FluentDSLCallTest.java
index 23c019083..8abf5b464 100644
--- a/experimental/lambda/src/test/java/io/serverless/workflow/impl/executors/func/FluentDSLCallTest.java
+++ b/experimental/lambda/src/test/java/io/serverless/workflow/impl/executors/func/FluentDSLCallTest.java
@@ -25,6 +25,8 @@
 import io.serverlessworkflow.impl.WorkflowApplication;
 import io.serverlessworkflow.impl.WorkflowDefinition;
 import io.serverlessworkflow.impl.WorkflowInstance;
+import io.serverlessworkflow.impl.WorkflowModel;
+import io.serverlessworkflow.impl.jackson.JsonUtils;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -131,4 +133,22 @@ void set_with_map() {
       assertEquals(Map.of("message", "hello world!"), output);
     }
   }
+
+  @Test
+  void set_with_string() {
+    try (WorkflowApplication app = WorkflowApplication.builder().build()) {
+      Workflow workflow =
+          FuncWorkflowBuilder.workflow()
+              .tasks(f -> f.set(s -> s.expr("{message:\"hello world!\"}")))
+              .build();
+
+      WorkflowDefinition workflowDefinition = app.workflowDefinition(workflow);
+
+      WorkflowModel model = workflowDefinition.instance(Map.of()).start().join();
+
+      assertEquals(
+          JsonUtils.mapper().createObjectNode().put("message", "hello world!"),
+          model.asJavaObject());
+    }
+  }
 }
diff --git a/fluent/spec/src/main/java/io/serverlessworkflow/fluent/spec/SetTaskBuilder.java b/fluent/spec/src/main/java/io/serverlessworkflow/fluent/spec/SetTaskBuilder.java
index 6ee2cbf8f..0ce11ec4a 100644
--- a/fluent/spec/src/main/java/io/serverlessworkflow/fluent/spec/SetTaskBuilder.java
+++ b/fluent/spec/src/main/java/io/serverlessworkflow/fluent/spec/SetTaskBuilder.java
@@ -21,8 +21,8 @@
 
 public class SetTaskBuilder extends TaskBaseBuilder<SetTaskBuilder> {
 
-  private final SetTask task;
-  private final SetTaskConfiguration setTaskConfiguration;
+  protected final SetTask task;
+  protected SetTaskConfiguration setTaskConfiguration;
 
   public SetTaskBuilder() {
     this.task = new SetTask();
@@ -49,7 +49,6 @@ public SetTask build() {
     if (this.task.getSet() == null) {
       this.task.setSet(new Set().withSetTaskConfiguration(setTaskConfiguration));
     }
-
     return task;
   }
 }