diff --git a/src/text-editor-element.coffee b/src/text-editor-element.coffee
index a5430cb5a..4a428178e 100644
--- a/src/text-editor-element.coffee
+++ b/src/text-editor-element.coffee
@@ -34,6 +34,7 @@ class TextEditorElement extends HTMLElement
       @stylesElement.initialize()
 
       @rootElement = document.createElement('div')
+      @rootElement.classList.add('shadow')
 
       @shadowRoot.appendChild(@stylesElement)
       @shadowRoot.appendChild(@rootElement)
diff --git a/static/text-editor-shadow.less b/static/text-editor-shadow.less
index 8187bdf93..c6d2ab57c 100644
--- a/static/text-editor-shadow.less
+++ b/static/text-editor-shadow.less
@@ -2,7 +2,11 @@
 @import "octicon-utf-codes";
 @import "octicon-mixins";
 
-.editor, .editor-contents {
+.editor-contents {
+  width: 100%;
+}
+
+.editor.shadow, .editor.shadow .editor-contents {
   height: 100%;
   width: 100%;
 }