diff --git a/edit/codemirror-default.js b/edit/codemirror-default.js
index a8832968..f9ead2b2 100644
--- a/edit/codemirror-default.js
+++ b/edit/codemirror-default.js
@@ -102,6 +102,7 @@
   }
 
   Object.assign(CodeMirror.mimeModes['text/css'].propertyKeywords, {
+    'contain': true,
     'mix-blend-mode': true,
     'isolation': true,
     // nonstandard https://compat.spec.whatwg.org/
diff --git a/vendor-overwrites/csslint/parserlib.js b/vendor-overwrites/csslint/parserlib.js
index 3e0e823c..dee5a93c 100644
--- a/vendor-overwrites/csslint/parserlib.js
+++ b/vendor-overwrites/csslint/parserlib.js
@@ -257,6 +257,7 @@ self.parserlib = (() => {
     'column-span':       'none | all',
     'column-width':      '<length> | auto',
     'columns':           1,
+    'contain':           'none | strict | content | [ size || layout || style || paint ]',
     'content':           'normal | none | <content-list> [ / <string> ]?',
     'counter-increment': 1,
     'counter-reset':     1,