diff --git a/src/core/jpg.js b/src/core/jpg.js
index 99bbf9e83..90ef8ade9 100644
--- a/src/core/jpg.js
+++ b/src/core/jpg.js
@@ -15,6 +15,7 @@
 
 import { assert, BaseException, warn } from "../shared/util.js";
 import { ColorSpaceUtils } from "./colorspace_utils.js";
+import { DeviceCmykCS } from "./colorspace.js";
 import { grayToRGBA } from "../shared/image_utils.js";
 import { readUint16 } from "./core_utils.js";
 
@@ -1349,6 +1350,13 @@ class JpegImage {
 
   _convertCmykToRgba(data) {
     ColorSpaceUtils.cmyk.getRgbBuffer(data, 0, data.length / 4, data, 0, 8, 1);
+
+    if (ColorSpaceUtils.cmyk instanceof DeviceCmykCS) {
+      // The alpha-component isn't updated by `DeviceCmykCS`, doing it manually.
+      for (let i = 3, ii = data.length; i < ii; i += 4) {
+        data[i] = 255;
+      }
+    }
     return data;
   }
 
diff --git a/test/test_manifest.json b/test/test_manifest.json
index f5e178215..a07b827bf 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -2960,6 +2960,15 @@
     "rounds": 1,
     "type": "eq"
   },
+  {
+    "id": "cmykjpeg_nowasm",
+    "file": "pdfs/cmykjpeg.pdf",
+    "md5": "85d162b48ce98503a382d96f574f70a2",
+    "link": false,
+    "rounds": 1,
+    "type": "eq",
+    "useWasm": false
+  },
   {
     "id": "issue4402_reduced",
     "file": "pdfs/issue4402_reduced.pdf",