diff --git a/external/dist/webpack.js b/external/dist/webpack.js
index d1e1f4250..6ac8fd69d 100644
--- a/external/dist/webpack.js
+++ b/external/dist/webpack.js
@@ -12,8 +12,17 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 "use strict";
 
+try {
+  require.resolve("worker-loader");
+} catch (ex) {
+  throw new Error(
+    "Cannot find the `worker-loader` package, please make sure that it's correctly installed."
+  );
+}
+
 var pdfjs = require("./build/pdf.js");
 var PdfjsWorker = require("worker-loader!./build/pdf.worker.js");
 
diff --git a/gulpfile.js b/gulpfile.js
index 60a9a4f8e..fcf570759 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -1548,12 +1548,6 @@ gulp.task(
         homepage: DIST_HOMEPAGE,
         bugs: DIST_BUGS_URL,
         license: DIST_LICENSE,
-        dependencies: {
-          "worker-loader": "^2.0.0", // used in external/dist/webpack.json
-        },
-        peerDependencies: {
-          webpack: "^3.0.0 || ^4.0.0-alpha.0 || ^4.0.0", // from 'worker-loader'
-        },
         browser: {
           fs: false,
           http: false,