diff --git a/calc.py b/calc.py
index bffda30de14fe151c13a448078fc0598652155d5..63dc5a41b0bed824384be61465a3894210ca4fd6 100644
--- a/calc.py
+++ b/calc.py
@@ -95,7 +95,7 @@ class Calc(QMainWindow):
         elif value in "+-*/":
             
             if self.x is None:
-                self.x = 0
+                self.x = '0'
             if self.x and self.y and self.operator:
                 self.calculate()
             self.operator = value