diff --git a/content/html/style/src/nsCSSKeywordList.h b/content/html/style/src/nsCSSKeywordList.h
index cff40f74a306..5b21bc6657d4 100644
--- a/content/html/style/src/nsCSSKeywordList.h
+++ b/content/html/style/src/nsCSSKeywordList.h
@@ -128,6 +128,7 @@ CSS_KEY(hiragana_iroha)
 CSS_KEY(horizontal)
 CSS_KEY(hz)
 CSS_KEY(icon)
+CSS_KEY(ignore)
 CSS_KEY(in)
 CSS_KEY(inactiveborder)
 CSS_KEY(inactivecaption)
diff --git a/content/shared/public/nsCSSKeywordList.h b/content/shared/public/nsCSSKeywordList.h
index cff40f74a306..5b21bc6657d4 100644
--- a/content/shared/public/nsCSSKeywordList.h
+++ b/content/shared/public/nsCSSKeywordList.h
@@ -128,6 +128,7 @@ CSS_KEY(hiragana_iroha)
 CSS_KEY(horizontal)
 CSS_KEY(hz)
 CSS_KEY(icon)
+CSS_KEY(ignore)
 CSS_KEY(in)
 CSS_KEY(inactiveborder)
 CSS_KEY(inactivecaption)
diff --git a/layout/html/style/src/nsCSSKeywordList.h b/layout/html/style/src/nsCSSKeywordList.h
index cff40f74a306..5b21bc6657d4 100644
--- a/layout/html/style/src/nsCSSKeywordList.h
+++ b/layout/html/style/src/nsCSSKeywordList.h
@@ -128,6 +128,7 @@ CSS_KEY(hiragana_iroha)
 CSS_KEY(horizontal)
 CSS_KEY(hz)
 CSS_KEY(icon)
+CSS_KEY(ignore)
 CSS_KEY(in)
 CSS_KEY(inactiveborder)
 CSS_KEY(inactivecaption)
diff --git a/layout/style/nsCSSKeywordList.h b/layout/style/nsCSSKeywordList.h
index cff40f74a306..5b21bc6657d4 100644
--- a/layout/style/nsCSSKeywordList.h
+++ b/layout/style/nsCSSKeywordList.h
@@ -128,6 +128,7 @@ CSS_KEY(hiragana_iroha)
 CSS_KEY(horizontal)
 CSS_KEY(hz)
 CSS_KEY(icon)
+CSS_KEY(ignore)
 CSS_KEY(in)
 CSS_KEY(inactiveborder)
 CSS_KEY(inactivecaption)