diff --git a/package-lock.json b/package-lock.json
index b4f1761f..49eaee25 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -28,7 +28,7 @@
         "@types/markup-js": "^1.5.0",
         "@types/mocha": "^10.0.10",
         "@types/node": "^24.10.0",
-        "@types/sinon": "^17.0.4",
+        "@types/sinon": "^21.0.0",
         "@vercel/ncc": "^0.38.3",
         "c8": "^10.1.3",
         "chai": "^6.2.0",
@@ -747,9 +747,9 @@
       "license": "MIT"
     },
     "node_modules/@types/sinon": {
-      "version": "17.0.4",
-      "resolved": "https://registry.npmjs.org/@types/sinon/-/sinon-17.0.4.tgz",
-      "integrity": "sha512-RHnIrhfPO3+tJT0s7cFaXGZvsL4bbR3/k7z3P312qMS4JaS2Tk+KiwiLx1S0rQ56ERj00u1/BtdyVd0FY+Pdew==",
+      "version": "21.0.0",
+      "resolved": "https://registry.npmjs.org/@types/sinon/-/sinon-21.0.0.tgz",
+      "integrity": "sha512-+oHKZ0lTI+WVLxx1IbJDNmReQaIsQJjN2e7UUrJHEeByG7bFeKJYsv1E75JxTQ9QKJDp21bAa/0W2Xo4srsDnw==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
diff --git a/package.json b/package.json
index 0a508ea2..1ec2911d 100644
--- a/package.json
+++ b/package.json
@@ -53,7 +53,7 @@
     "@types/markup-js": "^1.5.0",
     "@types/mocha": "^10.0.10",
     "@types/node": "^24.10.0",
-    "@types/sinon": "^17.0.4",
+    "@types/sinon": "^21.0.0",
     "@vercel/ncc": "^0.38.3",
     "c8": "^10.1.3",
     "chai": "^6.2.0",