diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa2786a5..e6c92a7f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
+## Unreleased
+
+### Fixed
+
+- Upload size limit is now enforced even when malware scanning is disabled (`scan: false`). Previously, `validateAttachmentSize` used `MAX_FILE_SIZE` as a function reference instead of calling it, and the function returned `-1` (no limit) when scanning was off — allowing arbitrarily large uploads on entities without `@Validation.Maximum`.
+
 ## Version 4.0.0 - 2026-08-03
 
 **BREAKING CHANGE: The attachments plugin comes now without hyperscaler dependencies, please make sure to install them accordingly!**
diff --git a/lib/generic-handlers.js b/lib/generic-handlers.js
index 05728034..2bf68687 100644
--- a/lib/generic-handlers.js
+++ b/lib/generic-handlers.js
@@ -1,7 +1,11 @@
 const cds = require("@sap/cds")
 const LOG = cds.log("attachments")
 const { extname } = require("path")
-const { MAX_FILE_SIZE, sizeInBytes, checkMimeTypeMatch } = require("./helper")
+const {
+  DEFAULT_MAX_FILE_SIZE,
+  sizeInBytes,
+  checkMimeTypeMatch,
+} = require("./helper")
 const { getMime } = require("./mime")
 
 /**
@@ -469,8 +473,8 @@ async function validateAttachmentSize(req, validateContentLength = false) {
 
   const maxFileSize = ctx.element["@Validation.Maximum"]
     ? (sizeInBytes(ctx.element["@Validation.Maximum"], req.target.name) ??
-      MAX_FILE_SIZE)
-    : MAX_FILE_SIZE
+      DEFAULT_MAX_FILE_SIZE)
+    : DEFAULT_MAX_FILE_SIZE
 
   const isInMemory =
     ctx.content != null && typeof ctx.content.length === "number"
diff --git a/lib/helper.js b/lib/helper.js
index 58c96af8..e3d7f26f 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -494,15 +494,7 @@ multipliers.PB = multipliers.TB * 1024
 multipliers.EB = multipliers.PB * 1024
 multipliers.ZB = multipliers.EB * 1024
 
-/**
- * Returns the maximum file size for uploads.
- * Returns -1 (no limit) when malware scanning is disabled, otherwise 400MB.
- * Evaluated at runtime to support dynamic configuration changes.
- * @returns {number} Maximum file size in bytes, or -1 for no limit
- */
-function MAX_FILE_SIZE() {
-  return cds.env.requires?.attachments?.scan == false ? -1 : 419430400 //400 MB in bytes
-}
+const DEFAULT_MAX_FILE_SIZE = 419430400 // 400 MB in bytes
 
 /**
  * Converts a byte size string into the corresponding number.
@@ -515,7 +507,7 @@ function sizeInBytes(size, target) {
     LOG.warn(
       `Could not determine the maximum byte size for the content of ${target}, falling back to default.`,
     )
-    return MAX_FILE_SIZE()
+    return DEFAULT_MAX_FILE_SIZE
   }
 
   if (typeof size === "number") {
@@ -527,7 +519,7 @@ function sizeInBytes(size, target) {
     LOG.warn(
       `Could not determine the maximum byte size for the content of ${target}, falling back to default.`,
     )
-    return MAX_FILE_SIZE()
+    return DEFAULT_MAX_FILE_SIZE
   }
 
   const unitMatches = size.toUpperCase().match(/([KMGTPEZ]I?)?B$/)
@@ -538,7 +530,7 @@ function sizeInBytes(size, target) {
     LOG.warn(
       `Could not determine the maximum byte size for the content of ${target}, falling back to default.`,
     )
-    return MAX_FILE_SIZE()
+    return DEFAULT_MAX_FILE_SIZE
   }
 
   return value * multipliers[unit]
@@ -917,7 +909,7 @@ module.exports = {
   checkMimeTypeMatch,
   traverseEntity,
   buildBackAssocChain,
-  MAX_FILE_SIZE,
+  DEFAULT_MAX_FILE_SIZE,
   getAttachmentKind,
   handleDuplicates,
   createSizeCheckHandler,
diff --git a/tests/unit/unitTests.test.js b/tests/unit/unitTests.test.js
index dd0db93f..4ecef004 100644
--- a/tests/unit/unitTests.test.js
+++ b/tests/unit/unitTests.test.js
@@ -16,7 +16,7 @@ const {
   getObjectStoreCredentials,
   fetchToken,
   sizeInBytes,
-  MAX_FILE_SIZE,
+  DEFAULT_MAX_FILE_SIZE,
   validateServiceManagerCredentials,
 } = require("../../lib/helper")
 
@@ -117,12 +117,8 @@ describe("fetchToken", () => {
 })
 
 describe("max attachment size", () => {
-  test("should return 400MB in normal scenario", () => {
-    expect(MAX_FILE_SIZE()).toEqual(400 * 1024 * 1024)
-  })
-  test("should return -1 when scan is disabled", () => {
-    cds.env.requires.attachments.scan = false
-    expect(MAX_FILE_SIZE()).toEqual(-1)
+  test("DEFAULT_MAX_FILE_SIZE is 400MB", () => {
+    expect(DEFAULT_MAX_FILE_SIZE).toEqual(400 * 1024 * 1024)
   })
 })
 
@@ -139,15 +135,12 @@ describe("size to byte converter", () => {
     expect(sizeInBytes(1234)).toEqual(1234)
   })
 
-  test("conversion of size string returns default MAX_FILE_SIZE if no size could be determined", () => {
-    // sizeInBytes returns MAX_FILE_SIZE (400MB = 419430400 bytes) as a safe default
-    // when the size cannot be determined
-    const MAX_FILE_SIZE = 419430400 // 400MB in bytes
-    expect(sizeInBytes("ABCDEFG")).toEqual(MAX_FILE_SIZE)
-
-    expect(sizeInBytes(undefined)).toEqual(MAX_FILE_SIZE)
-
-    expect(sizeInBytes({ $edmJson: "Dummy Value" })).toEqual(MAX_FILE_SIZE)
+  test("conversion of size string returns DEFAULT_MAX_FILE_SIZE if no size could be determined", () => {
+    expect(sizeInBytes("ABCDEFG")).toEqual(DEFAULT_MAX_FILE_SIZE)
+    expect(sizeInBytes(undefined)).toEqual(DEFAULT_MAX_FILE_SIZE)
+    expect(sizeInBytes({ $edmJson: "Dummy Value" })).toEqual(
+      DEFAULT_MAX_FILE_SIZE,
+    )
   })
 })