diff --git a/.eslintrc b/.eslintrc
index ac3506b6d32e0..4d0c7af71ee03 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -49,6 +49,8 @@
     "unicorn/no-new-buffer": "error",
     "unicorn/no-instanceof-array": "error",
     "unicorn/no-useless-spread": "error",
+    "unicorn/prefer-array-flat": "error",
+    "unicorn/prefer-array-flat-map": "error",
     "unicorn/prefer-at": "error",
     "unicorn/prefer-date-now": "error",
     "unicorn/prefer-dom-node-remove": "error",
diff --git a/src/core/xfa/som.js b/src/core/xfa/som.js
index 9015a81c4268f..02011b05aa744 100644
--- a/src/core/xfa/som.js
+++ b/src/core/xfa/som.js
@@ -254,7 +254,7 @@ function searchNode(
     if (isFinite(index)) {
       root = nodes.filter(node => index < node.length).map(node => node[index]);
     } else {
-      root = nodes.reduce((acc, node) => acc.concat(node), []);
+      root = nodes.flat();
     }
   }