diff --git a/client/src/proxguiqt.cpp b/client/src/proxguiqt.cpp
index 8da7378a6..241d3c419 100644
--- a/client/src/proxguiqt.cpp
+++ b/client/src/proxguiqt.cpp
@@ -780,6 +780,7 @@ Plot::Plot(QWidget *parent) : QWidget(parent), GraphPixelsPerPoint(1) {
 
     CursorAPos = 0;
     CursorBPos = 0;
+    GraphStart = 0;
     GraphStop = 0;
 
     setWindowTitle(tr("Sliders"));