diff --git a/package-lock.json b/package-lock.json
index 2eb653831..4d535ad2c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -72,7 +72,7 @@
     },
     "experimental/css-has-pseudo": {
       "name": "@csstools/css-has-pseudo-experimental",
-      "version": "0.1.0",
+      "version": "0.1.1",
       "license": "CC0-1.0",
       "dependencies": {
         "postcss-selector-parser": "^6.0.8"
@@ -4932,6 +4932,15 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/pify": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/pify/-/pify-2.3.0.tgz",
+      "integrity": "sha1-7RQaasBDqEnqWISY59yosVMw6Qw=",
+      "dev": true,
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/pkg-dir": {
       "version": "4.2.0",
       "resolved": "https://registry.npmjs.org/pkg-dir/-/pkg-dir-4.2.0.tgz",
@@ -5049,6 +5058,23 @@
       "resolved": "plugins/postcss-image-set-function",
       "link": true
     },
+    "node_modules/postcss-import": {
+      "version": "14.0.2",
+      "resolved": "https://registry.npmjs.org/postcss-import/-/postcss-import-14.0.2.tgz",
+      "integrity": "sha512-BJ2pVK4KhUyMcqjuKs9RijV5tatNzNa73e/32aBVE/ejYPe37iH+6vAu9WvqUkB5OAYgLHzbSvzHnorybJCm9g==",
+      "dev": true,
+      "dependencies": {
+        "postcss-value-parser": "^4.0.0",
+        "read-cache": "^1.0.0",
+        "resolve": "^1.1.7"
+      },
+      "engines": {
+        "node": ">=10.0.0"
+      },
+      "peerDependencies": {
+        "postcss": "^8.0.0"
+      }
+    },
     "node_modules/postcss-initial": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/postcss-initial/-/postcss-initial-4.0.1.tgz",
@@ -5299,6 +5325,15 @@
         "safe-buffer": "^5.1.0"
       }
     },
+    "node_modules/read-cache": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/read-cache/-/read-cache-1.0.0.tgz",
+      "integrity": "sha1-5mTvMRYRZsl1HNvo28+GtftY93Q=",
+      "dev": true,
+      "dependencies": {
+        "pify": "^2.3.0"
+      }
+    },
     "node_modules/readable-stream": {
       "version": "3.6.0",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.0.tgz",
@@ -6397,6 +6432,7 @@
       },
       "devDependencies": {
         "postcss": "^8.3.6",
+        "postcss-import": "^14.0.2",
         "postcss-tape": "^6.0.1"
       },
       "engines": {
@@ -10158,6 +10194,12 @@
       "integrity": "sha512-JU3teHTNjmE2VCGFzuY8EXzCDVwEqB2a8fsIvwaStHhAWJEeVd1o1QD80CU6+ZdEXXSLbSsuLwJjkCBWqRQUVA==",
       "dev": true
     },
+    "pify": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/pify/-/pify-2.3.0.tgz",
+      "integrity": "sha1-7RQaasBDqEnqWISY59yosVMw6Qw=",
+      "dev": true
+    },
     "pkg-dir": {
       "version": "4.2.0",
       "resolved": "https://registry.npmjs.org/pkg-dir/-/pkg-dir-4.2.0.tgz",
@@ -10219,6 +10261,7 @@
       "version": "file:plugins/postcss-custom-properties",
       "requires": {
         "postcss": "^8.3.6",
+        "postcss-import": "^14.0.2",
         "postcss-tape": "^6.0.1",
         "postcss-value-parser": "^4.2.0"
       }
@@ -10292,6 +10335,17 @@
         "postcss-value-parser": "^4.2.0"
       }
     },
+    "postcss-import": {
+      "version": "14.0.2",
+      "resolved": "https://registry.npmjs.org/postcss-import/-/postcss-import-14.0.2.tgz",
+      "integrity": "sha512-BJ2pVK4KhUyMcqjuKs9RijV5tatNzNa73e/32aBVE/ejYPe37iH+6vAu9WvqUkB5OAYgLHzbSvzHnorybJCm9g==",
+      "dev": true,
+      "requires": {
+        "postcss-value-parser": "^4.0.0",
+        "read-cache": "^1.0.0",
+        "resolve": "^1.1.7"
+      }
+    },
     "postcss-initial": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/postcss-initial/-/postcss-initial-4.0.1.tgz",
@@ -10528,6 +10582,15 @@
         "safe-buffer": "^5.1.0"
       }
     },
+    "read-cache": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/read-cache/-/read-cache-1.0.0.tgz",
+      "integrity": "sha1-5mTvMRYRZsl1HNvo28+GtftY93Q=",
+      "dev": true,
+      "requires": {
+        "pify": "^2.3.0"
+      }
+    },
     "readable-stream": {
       "version": "3.6.0",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.0.tgz",
diff --git a/plugins/postcss-custom-properties/.tape.js b/plugins/postcss-custom-properties/.tape.js
index e0589a6d5..c5593174f 100644
--- a/plugins/postcss-custom-properties/.tape.js
+++ b/plugins/postcss-custom-properties/.tape.js
@@ -1,3 +1,5 @@
+const importWithProps = require('./test/import');
+
 module.exports = {
 	'basic': {
 		message: 'supports basic usage'
@@ -311,5 +313,13 @@ module.exports = {
 		options: {
 			importFrom: {}
 		}
+	},
+	'import': {
+		message: 'supports "postcss-import"',
+		options: {
+			expect: 'import.expect.css',
+			result: 'import.result.css'
+		},
+		plugin: importWithProps
 	}
 };
diff --git a/plugins/postcss-custom-properties/package.json b/plugins/postcss-custom-properties/package.json
index 0ef854602..6a67c82ea 100644
--- a/plugins/postcss-custom-properties/package.json
+++ b/plugins/postcss-custom-properties/package.json
@@ -36,6 +36,7 @@
   },
   "devDependencies": {
     "postcss": "^8.3.6",
+    "postcss-import": "^14.0.2",
     "postcss-tape": "^6.0.1"
   },
   "peerDependencies": {
diff --git a/plugins/postcss-custom-properties/src/index.js b/plugins/postcss-custom-properties/src/index.js
index 7d755450a..cc750fc91 100755
--- a/plugins/postcss-custom-properties/src/index.js
+++ b/plugins/postcss-custom-properties/src/index.js
@@ -23,11 +23,12 @@ const creator = opts => {
 
 	return {
 		postcssPlugin: 'postcss-custom-properties',
-		prepare ({ root }) {
+		prepare () {
 			if (canReturnSyncFunction) {
-				customProperties = getCustomPropertiesFromRoot(root, { preserve });
-
 				return {
+					Once: (root) => {
+						customProperties = getCustomPropertiesFromRoot(root, { preserve });
+					},
 					Declaration: (decl) => transformProperties(decl, customProperties, { preserve }),
 				};
 			} else {
diff --git a/plugins/postcss-custom-properties/test/import.css b/plugins/postcss-custom-properties/test/import.css
new file mode 100644
index 000000000..64636398d
--- /dev/null
+++ b/plugins/postcss-custom-properties/test/import.css
@@ -0,0 +1,5 @@
+@import "./imported-file.css";
+
+a {
+	color: var(--color);
+}
diff --git a/plugins/postcss-custom-properties/test/import.expect.css b/plugins/postcss-custom-properties/test/import.expect.css
new file mode 100644
index 000000000..c7fcc0ac0
--- /dev/null
+++ b/plugins/postcss-custom-properties/test/import.expect.css
@@ -0,0 +1,8 @@
+:root {
+	--color: blue;
+}
+
+a {
+	color: blue;
+	color: var(--color);
+}
diff --git a/plugins/postcss-custom-properties/test/import.js b/plugins/postcss-custom-properties/test/import.js
new file mode 100644
index 000000000..34dcc2b23
--- /dev/null
+++ b/plugins/postcss-custom-properties/test/import.js
@@ -0,0 +1,12 @@
+const postcssImport = require('postcss-import');
+
+const importWithProps = () => {
+	return {
+		postcssPlugin: 'postcss-custom-properties (with postcss-import)',
+		plugins: [postcssImport(), require('../dist/index.cjs')()],
+	};
+};
+
+importWithProps.postcss = true;
+
+module.exports = importWithProps;
diff --git a/plugins/postcss-custom-properties/test/imported-file.css b/plugins/postcss-custom-properties/test/imported-file.css
new file mode 100644
index 000000000..eb0ff0d59
--- /dev/null
+++ b/plugins/postcss-custom-properties/test/imported-file.css
@@ -0,0 +1,3 @@
+:root {
+	--color: blue;
+}