From 3a5a0af48f4df77bae8f4c9df1eeddbee267e4f0 Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Tue, 6 Mar 2018 17:20:22 +0100
Subject: [PATCH] fix #4047

---
 gui/qt/main_window.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gui/qt/main_window.py b/gui/qt/main_window.py
index e0406df0a..6ced61be3 100644
--- a/gui/qt/main_window.py
+++ b/gui/qt/main_window.py
@@ -664,7 +664,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
             fiat_e.is_last_edited = (edit == fiat_e)
             amount = edit.get_amount()
             rate = self.fx.exchange_rate() if self.fx else None
-            if rate is None or amount is None:
+            if rate.is_nan() or amount is None:
                 if edit is fiat_e:
                     btc_e.setText("")
                     if fee_e: