diff --git a/src/Supporting/FileMakerRelation.php b/src/Supporting/FileMakerRelation.php
index ffafc8a..82c578d 100644
--- a/src/Supporting/FileMakerRelation.php
+++ b/src/Supporting/FileMakerRelation.php
@@ -217,6 +217,22 @@ public function __get($key)
         return $this->field($key);
     }
 
+    /**
+     * Handle the isset() function for the field or portal name.
+     * @param string $key The field or portal name.
+     * @return bool True if the field or portal exists.
+     * @ignore
+     */
+    public function __isset(string $key): bool
+    {
+        try {
+            $this->field($key);
+            return true;
+        } catch (Exception $e) {
+            return false;
+        }
+    }
+
     /**
      * Return the array of field names.
      *