diff --git a/web/base_viewer.js b/web/base_viewer.js
index affa751c4..f1932dc63 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -1173,7 +1173,7 @@ class BaseViewer {
         if (y === null && this._location) {
           x = this._location.left;
           y = this._location.top;
-        } else if (typeof y !== "number") {
+        } else if (typeof y !== "number" || y < 0) {
           // The "top" value isn't optional, according to the spec, however some
           // bad PDF generators will pretend that it is (fixes bug 1663390).
           y = pageHeight;