diff --git a/index.ts b/index.ts
index 710fbbd..f125d3b 100644
--- a/index.ts
+++ b/index.ts
@@ -139,7 +139,7 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 		let parts = []
 		for (let node of nodes) {
 			if (node.type === NODE.FUNCTION) {
-				let fn = node.name.toLowerCase()
+				let fn = node.name?.toLowerCase()
 				parts.push(fn, OPEN_PARENTHESES)
 				parts.push(print_list(node.children))
 				parts.push(CLOSE_PARENTHESES)
@@ -192,7 +192,7 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 			important.push(OPTIONAL_SPACE, text.slice(start, end).toLowerCase())
 		}
 		let value = print_value(node.value as CSSNode[] | null)
-		let property = node.property
+		let property = node.property!
 
 		// Special case for `font` shorthand: remove whitespace around /
 		if (property === 'font') {
@@ -262,9 +262,11 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 	}
 
 	function print_simple_selector(node: CSSNode, is_first: boolean = false): string {
+		let name = node.name ?? ''
+
 		switch (node.type) {
 			case NODE.TYPE_SELECTOR: {
-				return node.name.toLowerCase()
+				return name.toLowerCase() ?? ''
 			}
 
 			case NODE.COMBINATOR: {
@@ -280,7 +282,7 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 			case NODE.PSEUDO_ELEMENT_SELECTOR:
 			case NODE.PSEUDO_CLASS_SELECTOR: {
 				let parts = [COLON]
-				let name = node.name.toLowerCase()
+				name = name.toLowerCase()
 
 				// Legacy pseudo-elements or actual pseudo-elements use double colon
 				if (name === 'before' || name === 'after' || node.type === NODE.PSEUDO_ELEMENT_SELECTOR) {
@@ -305,7 +307,7 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 			}
 
 			case NODE.ATTRIBUTE_SELECTOR: {
-				let parts = [OPEN_BRACKET, node.name.toLowerCase()]
+				let parts = [OPEN_BRACKET, name.toLowerCase()]
 
 				if (node.attr_operator) {
 					parts.push(print_attribute_selector_operator(node.attr_operator))
@@ -507,7 +509,7 @@ export function format(css: string, { minify = false, tab_size = undefined }: Fo
 
 	function print_atrule(node: CSSNode): string {
 		let lines = []
-		let name = [`@`, node.name.toLowerCase()]
+		let name = [`@`, node.name!.toLowerCase()]
 		if (node.prelude) {
 			name.push(SPACE, print_atrule_prelude(node.prelude.text))
 		}
diff --git a/package-lock.json b/package-lock.json
index d84669f..c06154f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,7 +9,7 @@
 			"version": "2.2.2",
 			"license": "MIT",
 			"dependencies": {
-				"@projectwallace/css-parser": "^0.12.3"
+				"@projectwallace/css-parser": "^0.13.0"
 			},
 			"devDependencies": {
 				"@codecov/vite-plugin": "^1.9.1",
@@ -1150,9 +1150,9 @@
 			}
 		},
 		"node_modules/@projectwallace/css-parser": {
-			"version": "0.12.3",
-			"resolved": "https://registry.npmjs.org/@projectwallace/css-parser/-/css-parser-0.12.3.tgz",
-			"integrity": "sha512-ZET2NGXZpqHHQmjV9sVIc0Vmgn8v2Xtg8KejKDNhKNsqGySyNMBJrIEEMhkofqrNU72zxaNubfVf4nk+F9dBJA==",
+			"version": "0.13.0",
+			"resolved": "https://registry.npmjs.org/@projectwallace/css-parser/-/css-parser-0.13.0.tgz",
+			"integrity": "sha512-kXoXv7yh/xUBSxADh8H/JADV56S3hQe/vkRqQGAbrCcxu4m0nBkgSnsfIYzMAdCgazG94dCHzNzNR+2nNfSvEA==",
 			"license": "MIT"
 		},
 		"node_modules/@publint/pack": {
diff --git a/package.json b/package.json
index 3c1203b..1073c0f 100644
--- a/package.json
+++ b/package.json
@@ -60,6 +60,6 @@
 		"singleQuote": true
 	},
 	"dependencies": {
-		"@projectwallace/css-parser": "^0.12.3"
+		"@projectwallace/css-parser": "^0.13.0"
 	}
 }