diff --git a/docs/callbacks.md b/docs/callbacks.md
index 921aa6fd3d..233ef7ec06 100644
--- a/docs/callbacks.md
+++ b/docs/callbacks.md
@@ -229,7 +229,10 @@ $label->link($cb->getUrl());
 When you trigger callback, you'll see the output:
 
 ```
-{"success": true, "message": "Success", "eval": "alert(\"ok\")"}
+{
+    "success": true,
+    "atkjs": "alert(\"ok\");"
+}
 ```
 
 This is how JsCallback renders actions and sends them back to the browser. In order to retrieve and execute actions,
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 3c18aae495..f98aab2463 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -399,4 +399,7 @@ parameters:
             message: '~^Parameter #1 \$object of method Atk4\\Ui\\App::add\(\) expects Atk4\\Ui\\AbstractView, array given\.$~'
         -
             path: 'src/Popup.php'
-            message: '~^Parameter #1 \$view of method Atk4\\Ui\\Callback::terminateJson\(\) expects Atk4\\Ui\\View, Atk4\\Ui\\AbstractView given\.$~'
+            message: '~^Parameter #1 \$ of closure expects Atk4\\Ui\\View, Atk4\\Ui\\AbstractView given\.$~'
+        -
+            path: 'src/Popup.php'
+            message: '~^Parameter #1 \$view of method Atk4\\Ui\\Callback::terminateJsonIfCanTerminate\(\) expects Atk4\\Ui\\View, Atk4\\Ui\\AbstractView given\.$~'
diff --git a/src/Callback.php b/src/Callback.php
index 8869d394a8..fe94f7ddf3 100644
--- a/src/Callback.php
+++ b/src/Callback.php
@@ -89,7 +89,7 @@ public function set($fx = null, $fxArgs = null)
     /**
      * Terminate this callback by rendering the given view.
      */
-    public function terminateJson(View $view): void
+    public function terminateJsonIfCanTerminate(View $view): void
     {
         if ($this->canTerminate()) {
             $this->getApp()->terminateJson($view);
diff --git a/src/Form/Control/Multiline.php b/src/Form/Control/Multiline.php
index d19659f573..f836a5d907 100644
--- a/src/Form/Control/Multiline.php
+++ b/src/Form/Control/Multiline.php
@@ -685,9 +685,9 @@ private function outputJson(): void
                 // no break - expression above always terminate
             case 'on-change':
                 $rowsRaw = $this->getApp()->decodeJson($this->getApp()->getRequestPostParam('rows'));
-                $response = ($this->onChangeFunction)($this->typeCastLoadValues($rowsRaw), $this->form);
-                $this->renderCallback->terminateAjax($this->renderCallback->getAjaxec($response));
-                // TODO JsCallback::terminateAjax() should return never
+                $this->renderCallback->set(function () use ($rowsRaw) {
+                    return ($this->onChangeFunction)($this->typeCastLoadValues($rowsRaw), $this->form);
+                });
         }
     }
 
diff --git a/src/JsCallback.php b/src/JsCallback.php
index 87d207431a..4ab03d722a 100644
--- a/src/JsCallback.php
+++ b/src/JsCallback.php
@@ -93,7 +93,7 @@ public function set($fx = null, $args = null)
 
             $ajaxec = $this->getAjaxec($response);
 
-            $this->terminateAjax($ajaxec);
+            $this->terminateAjaxIfCanTerminate($ajaxec);
         });
 
         return $this;
@@ -102,17 +102,13 @@ public function set($fx = null, $args = null)
     /**
      * A proper way to finish execution of AJAX response. Generates JSON
      * which is returned to frontend.
-     *
-     * @param ($success is true ? null : string) $msg     General message, typically won't be displayed
-     * @param bool                               $success Was request successful or not
      */
-    public function terminateAjax(JsBlock $ajaxec, $msg = null, bool $success = true): void
+    protected function terminateAjaxIfCanTerminate(JsBlock $ajaxec): void
     {
-        $data = ['success' => $success];
-        if (!$success) {
-            $data['message'] = $msg;
-        }
-        $data['atkjs'] = $ajaxec->jsRender();
+        $data = [
+            'success' => true,
+            'atkjs' => $ajaxec->jsRender(),
+        ];
 
         if ($this->canTerminate()) {
             $this->getApp()->terminateJson($data);
diff --git a/src/JsSse.php b/src/JsSse.php
index ca55bf93bd..66db2b8de8 100644
--- a/src/JsSse.php
+++ b/src/JsSse.php
@@ -83,13 +83,13 @@ protected function initSse(): void
     /**
      * Sending an SSE action.
      */
-    public function send(JsExpressionable $action, bool $success = true): void
+    public function send(JsExpressionable $action): void
     {
         $ajaxec = $this->getAjaxec($action);
         $this->sendEvent(
             '',
             $this->getApp()->encodeJson([
-                'success' => $success,
+                'success' => true,
                 'atkjs' => $ajaxec->jsRender(),
             ]),
             'atkSseAction'
@@ -100,14 +100,14 @@ public function send(JsExpressionable $action, bool $success = true): void
      * @return never
      */
     #[\Override]
-    public function terminateAjax(JsBlock $ajaxec, $msg = null, bool $success = true): void
+    protected function terminateAjaxIfCanTerminate(JsBlock $ajaxec): void
     {
         $ajaxecStr = $ajaxec->jsRender();
         if ($ajaxecStr !== '') {
             $this->sendEvent(
                 '',
                 $this->getApp()->encodeJson([
-                    'success' => $success,
+                    'success' => true,
                     'atkjs' => $ajaxecStr,
                 ]),
                 'atkSseAction'
diff --git a/src/Loader.php b/src/Loader.php
index 7b78ac2e93..d3c471adad 100644
--- a/src/Loader.php
+++ b/src/Loader.php
@@ -85,7 +85,8 @@ public function set($fx = null)
 
         $this->cb->set(function () use ($fx) {
             $fx($this);
-            $this->cb->terminateJson($this->getShimIfOwner());
+
+            $this->cb->terminateJsonIfCanTerminate($this->getShimIfOwner());
         });
 
         return $this;
diff --git a/src/Modal.php b/src/Modal.php
index 4895b50b76..9bd6815873 100644
--- a/src/Modal.php
+++ b/src/Modal.php
@@ -98,7 +98,8 @@ public function enableCallback(): void
 
         $this->cb->set(function () {
             ($this->fx)($this->cbView);
-            $this->cb->terminateJson($this->cbView);
+
+            $this->cb->terminateJsonIfCanTerminate($this->cbView);
         });
     }
 
diff --git a/src/Panel/Content.php b/src/Panel/Content.php
index 563705d425..fa931d5bf8 100644
--- a/src/Panel/Content.php
+++ b/src/Panel/Content.php
@@ -50,7 +50,8 @@ public function onLoad(\Closure $fx): void
     {
         $this->cb->set(function () use ($fx) {
             $fx($this);
-            $this->cb->terminateJson($this);
+
+            $this->cb->terminateJsonIfCanTerminate($this);
         });
     }
 
diff --git a/src/Popup.php b/src/Popup.php
index b194682b67..583a08b805 100644
--- a/src/Popup.php
+++ b/src/Popup.php
@@ -145,12 +145,15 @@ public function set($fx = null)
             $this->minHeight = '45px';
         }
 
-        // create content view to pass to callback
-        $content = $this->add($this->dynamicContent);
-        $this->cb->set($fx, [$content]);
-        // only render our content view
-        // PopupService will replace content with this one
-        $this->cb->terminateJson($content);
+        $this->cb->set(function () use ($fx) {
+            // create content view to pass to callback
+            $content = $this->add($this->dynamicContent);
+
+            $fx($content);
+
+            // only render our content view, PopupService will replace content with this one
+            $this->cb->terminateJsonIfCanTerminate($content);
+        });
 
         return $this;
     }