diff --git a/src/Extension/ExtendableTrait.php b/src/Extension/ExtendableTrait.php
index 2855d187..f899d669 100644
--- a/src/Extension/ExtendableTrait.php
+++ b/src/Extension/ExtendableTrait.php
@@ -210,7 +210,6 @@ public function addDynamicProperty($dynamicName, $value = null)
         self::$extendableGuardProperties = false;
 
         array_set($this->extensionData['dynamicProperties'], $dynamicName, $value);
-        $this->extendableSet($dynamicName, $value);
 
         self::$extendableGuardProperties = true;
     }
@@ -419,7 +418,7 @@ public function extendableSet($name, $value)
          * Setting an undefined property
          */
         if (!self::$extendableGuardProperties) {
-            $this->{$name} = $value;
+            array_set($this->extensionData['dynamicProperties'], $name, $value);
         }
     }
 
diff --git a/src/Halcyon/Model.php b/src/Halcyon/Model.php
index c130823a..4129f5bf 100644
--- a/src/Halcyon/Model.php
+++ b/src/Halcyon/Model.php
@@ -1603,6 +1603,15 @@ public static function cacheMutatedAttributes($class)
         static::$mutatorCache[$class] = $mutatedAttributes;
     }
 
+    public function addDynamicProperty($dynamicName, $value = null)
+    {
+        if (isset($this->attributes[$dynamicName])) {
+            return;
+        }
+
+        $this->setAttribute($dynamicName, $value);
+    }
+
     /**
      * Dynamically retrieve attributes on the model.
      *