diff --git a/typings/xterm.d.ts b/typings/xterm.d.ts
index 19f2b784..10bd255f 100644
--- a/typings/xterm.d.ts
+++ b/typings/xterm.d.ts
@@ -290,7 +290,9 @@ declare module 'xterm' {
 
     /**
      * Opens the terminal within an element.
-     * @param parent The element to create the terminal within.
+     * @param parent The element to create the terminal within. This element
+     * must be visible (have dimensions) when `open` is called as several DOM-
+     * based measurements need to be performed when this function is called.
      */
     open(parent: HTMLElement): void;