diff --git a/after/syntax/css/conditional-5.vim b/after/syntax/css/conditional-5.vim
index 1a2e61c..3c2a5a3 100644
--- a/after/syntax/css/conditional-5.vim
+++ b/after/syntax/css/conditional-5.vim
@@ -1,3 +1,3 @@
 syn keyword cssFontProp contained container-type container-name container
 syn keyword cssFontAttr contained inline-size
-syn match cssFontDescriptor "@\(when\|else\)\>" nextgroup=cssFontDescriptorBlock skipwhite skipnl
+syn match cssFontDescriptor "@\(when\|else\|supports-condition\)\>" nextgroup=cssFontDescriptorBlock skipwhite skipnl
diff --git a/test/test.css b/test/test.css
index a570609..aa362a3 100644
--- a/test/test.css
+++ b/test/test.css
@@ -273,6 +273,12 @@
   }
 }
 
+@supports-condition --thicker-underlines {
+  .conditional-5 {
+    display: auto;
+  }
+}
+
 .contain-1 {
   contain: auto;
   display: layout;