diff --git a/package-lock.json b/package-lock.json
index 5ef9febda..33fc7d4d3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -31,7 +31,7 @@
         "express-static-gzip": "^2.1.7",
         "fnv-plus": "^1.3.1",
         "govuk-frontend": "^5.2.0",
-        "happy-dom": "^14.3.9",
+        "happy-dom": "^15.8.3",
         "helmet": "^7.1.0",
         "html-entities": "^2.5.2",
         "jsdom": "^24.0.0",
@@ -8652,16 +8652,16 @@
       }
     },
     "node_modules/happy-dom": {
-      "version": "14.3.9",
-      "resolved": "https://registry.npmjs.org/happy-dom/-/happy-dom-14.3.9.tgz",
-      "integrity": "sha512-0kPQchwthekcYpYN8CvCiq+/z5bqFYDLbTxZ+yDLwT8AFRVJDFadShHRxp3VAZRy7a5isOZ1j/LzsU1dtAIZMQ==",
+      "version": "15.8.3",
+      "resolved": "https://registry.npmjs.org/happy-dom/-/happy-dom-15.8.3.tgz",
+      "integrity": "sha512-YR9nUWN/T2bH7pPLEYMhTp4DQExPH+mC4KulJDgimCb+FY3Er0Vp6SOOcBXrNfMTri3lAk9uSZqUTG2hgZOYwg==",
       "dependencies": {
         "entities": "^4.5.0",
         "webidl-conversions": "^7.0.0",
         "whatwg-mimetype": "^3.0.0"
       },
       "engines": {
-        "node": ">=16.0.0"
+        "node": ">=18.0.0"
       }
     },
     "node_modules/har-schema": {
diff --git a/package.json b/package.json
index 1bf712579..6cc5040b2 100644
--- a/package.json
+++ b/package.json
@@ -117,7 +117,7 @@
     "express-static-gzip": "^2.1.7",
     "fnv-plus": "^1.3.1",
     "govuk-frontend": "^5.2.0",
-    "happy-dom": "^14.3.9",
+    "happy-dom": "^15.8.3",
     "helmet": "^7.1.0",
     "html-entities": "^2.5.2",
     "jsdom": "^24.0.0",