diff --git a/.circleci/config.yml b/.circleci/config.yml
index ad965b33..7365d027 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -100,6 +100,7 @@ commands:
           command: npm run test:coverage -- --ci --reporters=default --reporters=jest-junit <<#parameters.runInBand>>-i<</parameters.runInBand>><<^parameters.runInBand>>--maxWorkers=2<</parameters.runInBand>>
           environment:
             CHROME_DISABLE_GPU: 1 # Disable GPU acceleration to mitigate flaky tests
+            DEBUG: marp-cli:jpeg
             JEST_JUNIT_CLASSNAME: '{filepath}'
             JEST_JUNIT_OUTPUT_DIR: tmp/test-results
             MARP_TEST_CI: 1
diff --git a/.github/workflows/test-win.yml b/.github/workflows/test-win.yml
index 61ab1bc4..ea4bbf63 100644
--- a/.github/workflows/test-win.yml
+++ b/.github/workflows/test-win.yml
@@ -49,6 +49,7 @@ jobs:
       - name: Jest
         env:
           CHROME_DISABLE_GPU: 1 # Disable GPU acceleration to mitigate flaky tests
+          DEBUG: marp-cli:jpeg
           JEST_JUNIT_CLASSNAME: '{filepath}'
           JEST_JUNIT_OUTPUT_DIR: tmp/test-results
           MARP_TEST_CI: 1
diff --git a/src/utils/jpeg.ts b/src/utils/jpeg.ts
index e1ead540..a982c998 100644
--- a/src/utils/jpeg.ts
+++ b/src/utils/jpeg.ts
@@ -1,5 +1,7 @@
+import dbg from 'debug'
 import { Browser } from '../browser/browser'
-import { debug } from './debug'
+
+const debug = dbg('marp-cli:jpeg')
 
 export const png2jpegViaPuppeteer = async (
   browser: Browser,
@@ -13,6 +15,8 @@ export const png2jpegViaPuppeteer = async (
       waitUntil: ['domcontentloaded', 'networkidle0'],
     })
 
+    debug('Evaluating JavaScript to convert PNG to JPEG')
+
     const jpegDataURL = await page.evaluate(
       async (pngUri, q, timeout) => {
         /* c8 ignore start */
@@ -52,6 +56,8 @@ export const png2jpegViaPuppeteer = async (
       browser.timeout
     )
 
+    debug('Evaluated JavaScript to convert PNG to JPEG')
+
     if (!jpegDataURL.startsWith('data:image/jpeg;base64,'))
       throw new Error('Failed to convert PNG to JPEG')