diff --git a/after/syntax/css/css-flexbox-1.vim b/after/syntax/css/css-flexbox-1.vim
index 94da896..c6e511e 100644
--- a/after/syntax/css/css-flexbox-1.vim
+++ b/after/syntax/css/css-flexbox-1.vim
@@ -3,4 +3,3 @@ syn match cssFontProp contained "\<flex\(-\(basis\|direction\|flow\|grow\|shrink
 syn keyword cssFontAttr contained flex row wrap
 syn match cssFontAttr contained "\<inline-flex\>"
 syn match cssFontAttr contained "\<\(row\|column\|wrap\)-reverse\>"
-syn match cssFontAttr contained "\<main-size\>"
diff --git a/test/test.css b/test/test.css
index 9ca714c..870bb94 100644
--- a/test/test.css
+++ b/test/test.css
@@ -222,7 +222,6 @@
   flex: column-reverse;
   flex-grow: wrap;
   flex-shrink: wrap-reverse;
-  flex-basis: main-size;
 }
 
 .font-loading-3 {
diff --git a/test/test.html b/test/test.html
index c38a5e9..a11f8a1 100644
--- a/test/test.html
+++ b/test/test.html
@@ -251,7 +251,6 @@
   flex: column-reverse;
   flex-grow: wrap;
   flex-shrink: wrap-reverse;
-  flex-basis: main-size;
 }
 </style>
 <style>