diff --git a/chrome/content/zotero/xpcom/reader.js b/chrome/content/zotero/xpcom/reader.js
index cbf8dedb74..7bc6a8b537 100644
--- a/chrome/content/zotero/xpcom/reader.js
+++ b/chrome/content/zotero/xpcom/reader.js
@@ -183,7 +183,13 @@ class ReaderInstance {
 				return uri.scheme === 'http' || uri.scheme === 'https';
 			}
 		});
-		this._blockingObserver.register(this._iframe);
+		try {
+			this._blockingObserver.register(this._iframe);
+		}
+		catch {
+			// Reader was closed before it could be initialized
+			// No need to log this
+		}
 
 		this._internalReader = this._iframeWindow.wrappedJSObject.createReader(Components.utils.cloneInto({
 			type: this._type,