diff --git a/lib/js/dom.nim b/lib/js/dom.nim
index a133f1f69a..303cc178f6 100644
--- a/lib/js/dom.nim
+++ b/lib/js/dom.nim
@@ -1496,7 +1496,9 @@ proc find*(w: Window, text: cstring, caseSensitive = false,
            backwards = false)
 proc focus*(w: Window)
 proc forward*(w: Window)
-proc getComputedStyle*(w: Window, e: Node, pe:Node = nil): Style
+proc getComputedStyle*(w: Window, e: Node, pe: Node = nil): Style
+  ## .. warning:: The returned Style may or may not be read-only at run-time in the browser. getComputedStyle is performance costly.
+
 proc handleEvent*(w: Window, e: Event)
 proc home*(w: Window)
 proc moveBy*(w: Window, x, y: int)