diff --git a/src/esi.cls.php b/src/esi.cls.php
index 55333dba2..25e724acb 100644
--- a/src/esi.cls.php
+++ b/src/esi.cls.php
@@ -825,6 +825,8 @@ public function load_admin_bar_block($params)
 				}
 			}
 		}
+		// Needed when permalink structure is "Plain"
+		wp();
 
 		wp_admin_bar_render();
 		if (!$this->conf(Base::O_ESI_CACHE_ADMBAR)) {