diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index fdf2ed5..5f65ddc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [16.x, 18.x, 20.x, 22.x]
+        node-version: [18.x, 20.x, 22.x]
     steps:
     - uses: actions/checkout@v4
     - name: Use Node.js ${{ matrix.node-version }}
diff --git a/package.json b/package.json
index cbb4009..ae6ecbd 100644
--- a/package.json
+++ b/package.json
@@ -20,6 +20,15 @@
     "prepublishOnly": "EXPRESS_MAJOR=4 mocha && EXPRESS_MAJOR=5 mocha",
     "postpublish": "git push origin && git push origin --tags"
   },
+  "peerDependencies": {
+    "express": ">= 4.17.3 < 6.0.0"
+  },
+  "peerDependenciesMeta": {
+    "express": {
+      "optional": true,
+      "meta": "This package imports `router`, which comes with `express`."
+    }
+  },
   "devDependencies": {
     "express": "^4.18.2",
     "express4": "github:expressjs/express#4.19.2",
@@ -34,7 +43,6 @@
     "ajv-keywords": "^5.1.0",
     "http-errors": "^2.0.0",
     "path-to-regexp": "^6.2.1",
-    "router": "^1.3.8",
     "serve-static": "^1.15.0",
     "swagger-parser": "^10.0.3",
     "swagger-ui-dist": "^5.11.8",