diff --git a/web/pdf_thumbnail_view.js b/web/pdf_thumbnail_view.js
index 2cf3f6c5c..c990cc467 100644
--- a/web/pdf_thumbnail_view.js
+++ b/web/pdf_thumbnail_view.js
@@ -352,13 +352,17 @@ class PDFThumbnailView {
     if (this.renderingState !== RenderingStates.INITIAL) {
       return;
     }
-    const { thumbnailCanvas: canvas, pdfPage } = pageView;
+    const { thumbnailCanvas: canvas, pdfPage, scale } = pageView;
     if (!canvas) {
       return;
     }
     if (!this.pdfPage) {
       this.setPdfPage(pdfPage);
     }
+    if (scale < this.scale) {
+      // Avoid upscaling the image, since that makes the thumbnail look blurry.
+      return;
+    }
     this.renderingState = RenderingStates.FINISHED;
     this._convertCanvasToImage(canvas);
   }