diff --git a/lib/reference/keywordSets.js b/lib/reference/keywordSets.js
index efbb0affe6..b5ed5abfbf 100644
--- a/lib/reference/keywordSets.js
+++ b/lib/reference/keywordSets.js
@@ -179,6 +179,8 @@ keywordSets.shadowTreePseudoElements = new Set(['part']);
 
 keywordSets.vendorSpecificPseudoElements = new Set([
 	'-moz-focus-inner',
+	'-moz-focus-outer',
+	'-moz-placeholder',
 	'-moz-progress-bar',
 	'-moz-range-progress',
 	'-moz-range-thumb',
@@ -197,6 +199,7 @@ keywordSets.vendorSpecificPseudoElements = new Set([
 	'-ms-tooltip',
 	'-ms-track',
 	'-ms-value',
+	'-webkit-input-placeholder',
 	'-webkit-progress-bar',
 	'-webkit-progress-value',
 	'-webkit-slider-runnable-track',
@@ -231,11 +234,6 @@ keywordSets.otherPseudoClasses = new Set([
 	'autofill',
 	'blank',
 	'checked',
-	/*
-	  https://www.w3.org/Style/CSS/Test/CSS3/Selectors/20011105/html/tests/css3-modsel-85.html
-	  https://www.w3.org/Style/CSS/Test/CSS3/Selectors/20011105/html/tests/css3-modsel-84.html
-	*/
-	'contains',
 	'current',
 	'default',
 	'defined',
@@ -256,7 +254,6 @@ keywordSets.otherPseudoClasses = new Set([
 	'hover',
 	'indeterminate',
 	'in-range',
-	'invalid',
 	'last-child',
 	'last-of-type',
 	'link',
@@ -275,12 +272,22 @@ keywordSets.otherPseudoClasses = new Set([
 	'scope',
 	'state',
 	'target',
-	'user-error',
 	'user-invalid',
+	'user-valid',
+	'invalid',
 	'valid',
 	'visited',
 ]);
 
+keywordSets.vendorSpecificPseudoClasses = new Set([
+	'-moz-placeholder',
+	'-moz-ui-invalid',
+	'-moz-ui-valid',
+	'-ms-input-placeholder',
+]);
+
+// TODO migrate to vendorSpecificPseudoElements
+// see #2264
 keywordSets.webkitProprietaryPseudoElements = new Set([
 	'scrollbar',
 	'scrollbar-button',
@@ -291,6 +298,8 @@ keywordSets.webkitProprietaryPseudoElements = new Set([
 	'resize',
 ]);
 
+// TODO migrate to vendorSpecificPseudoClasses
+// see #2264
 keywordSets.webkitProprietaryPseudoClasses = new Set([
 	'horizontal',
 	'vertical',
@@ -311,6 +320,7 @@ keywordSets.pseudoClasses = uniteSets(
 	keywordSets.logicalCombinationsPseudoClasses,
 	keywordSets.aNPlusBOfSNotationPseudoClasses,
 	keywordSets.otherPseudoClasses,
+	keywordSets.vendorSpecificPseudoClasses,
 );
 
 keywordSets.shorthandTimeProperties = new Set(['transition', 'animation']);