diff --git a/gui/qt/main_window.py b/gui/qt/main_window.py
index 3cf27d04c..cd46e8908 100644
--- a/gui/qt/main_window.py
+++ b/gui/qt/main_window.py
@@ -1053,6 +1053,8 @@ class ElectrumWindow(QMainWindow):
 
         # sign the tx
         def sign_thread():
+            if self.wallet.is_watching_only():
+                return tx
             keypairs = {}
             try:
                 self.wallet.add_keypairs(tx, keypairs, password)