diff --git a/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.test.ts b/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.test.ts
index 70a12187d2..1d6e9fff20 100644
--- a/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.test.ts
+++ b/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.test.ts
@@ -316,4 +316,44 @@ describe('copyConfigKeyEntry', () => {
       await expect(fileExists(joinPath(outDir, 'tools.json'))).resolves.toBe(true)
     })
   })
+
+  describe('value guard', () => {
+    test('throws when value is an empty string', async () => {
+      await inTemporaryDirectory(async (tmpDir) => {
+        const outDir = joinPath(tmpDir, 'out')
+        await mkdir(outDir)
+        const context = makeContext({assets: ''})
+        const promise = copyConfigKeyEntry({key: 'assets', baseDir: tmpDir, outputDir: outDir, context})
+        await expect(promise).rejects.toThrow(AbortError)
+        await expect(promise).rejects.toThrow(`'assets' can't be empty.`)
+      })
+    })
+
+    test('throws when value is whitespace-only', async () => {
+      await inTemporaryDirectory(async (tmpDir) => {
+        const outDir = joinPath(tmpDir, 'out')
+        await mkdir(outDir)
+        const context = makeContext({assets: '   '})
+        const promise = copyConfigKeyEntry({key: 'assets', baseDir: tmpDir, outputDir: outDir, context})
+        await expect(promise).rejects.toThrow(AbortError)
+        await expect(promise).rejects.toThrow(`'assets' can't be empty.`)
+      })
+    })
+
+    test('throws with the field name only, not the full configKey, when the key is nested', async () => {
+      await inTemporaryDirectory(async (tmpDir) => {
+        const outDir = joinPath(tmpDir, 'out')
+        await mkdir(outDir)
+        const context = makeContext({extension_points: [{assets: ''}]})
+        const promise = copyConfigKeyEntry({
+          key: 'extension_points[].assets',
+          baseDir: tmpDir,
+          outputDir: outDir,
+          context,
+        })
+        await expect(promise).rejects.toThrow(AbortError)
+        await expect(promise).rejects.toThrow(`'assets' can't be empty.`)
+      })
+    })
+  })
 })
diff --git a/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.ts b/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.ts
index edb9b9e6b3..96e7098efe 100644
--- a/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.ts
+++ b/packages/app/src/cli/services/build/steps/include-assets/copy-config-key-entry.ts
@@ -48,6 +48,13 @@ export async function copyConfigKeyEntry(config: {
     paths = []
   }
 
+  for (const sourcePath of paths) {
+    if (sourcePath.trim() === '') {
+      const fieldName = key.split('.').pop()?.replace(/\[\]$/, '') ?? key
+      throw new AbortError(`'${fieldName}' can't be empty.`)
+    }
+  }
+
   if (paths.length === 0) {
     outputDebug(`No value for configKey '${key}', skipping\n`, stdout)
     return {filesCopied: 0, pathMap: new Map()}