diff --git a/after/syntax/css/shadow-parts-1.vim b/after/syntax/css/shadow-parts-1.vim
new file mode 100644
index 0000000..11039d4
--- /dev/null
+++ b/after/syntax/css/shadow-parts-1.vim
@@ -0,0 +1 @@
+syn region cssPseudoClassLang matchgroup=cssPseudoClassId start=":part(" end=")" oneline
diff --git a/test/test.css b/test/test.css
index 2b03c6e..358a52c 100644
--- a/test/test.css
+++ b/test/test.css
@@ -778,6 +778,10 @@ mask {
   display: auto;
 }
 
+.shadow-parts::part(textspan) {
+  display: auto;
+}
+
 .shapes-1 {
   shape-outside: auto;
   shape-image-threshold: auto;