diff --git a/artiq/applets/plot_xy.py b/artiq/applets/plot_xy.py
index 413d90cb2..6502a004d 100755
--- a/artiq/applets/plot_xy.py
+++ b/artiq/applets/plot_xy.py
@@ -45,7 +45,8 @@ class XYPlot(pyqtgraph.PlotWidget):
             errbars = pg.ErrorBarItem(x=np.array(x), y=np.array(y), height=error)
             self.addItem(errbars)
         if fit is not None:
-            self.plot(x, fit)
+            xi = np.argsort(x)
+            self.plot(x[xi], fit[xi])
 
 
 def main():