diff --git a/frontend/src/lib/components/PdfViewer.svelte b/frontend/src/lib/components/PdfViewer.svelte
index d22ca2b4..6514b707 100644
--- a/frontend/src/lib/components/PdfViewer.svelte
+++ b/frontend/src/lib/components/PdfViewer.svelte
@@ -141,7 +141,10 @@ $effect(() => {
 });
 
 $effect(() => {
-	if (pdfDoc && currentPage) {
+	// Read scale synchronously so Svelte tracks it as a dependency.
+	// Without this, zoom changes don't re-trigger the effect because
+	// scale is only read inside the async renderPage call.
+	if (pdfDoc && currentPage && scale > 0) {
 		renderPage(pdfDoc, currentPage).then(() => {
 			if (pdfDoc) prerender(pdfDoc, currentPage);
 		});