2 files changed, 12 insertions, 4 deletions
diff --git a/client/src/com/vaadin/client/ui/calendar/schedule/DateCellDayEvent.java b/client/src/com/vaadin/client/ui/calendar/schedule/DateCellDayEvent.java
index 1a54fe0454..55834397d3 100644
--- a/client/src/com/vaadin/client/ui/calendar/schedule/DateCellDayEvent.java
+++ b/client/src/com/vaadin/client/ui/calendar/schedule/DateCellDayEvent.java
@@ -268,8 +268,13 @@ public class DateCellDayEvent extends FocusableHTML implements
         }
         int endX = event.getClientX();
         int endY = event.getClientY();
-        int xDiff = startX - endX;
-        int yDiff = startY - endY;
+        int xDiff = 0, yDiff = 0;
+        if (startX != -1 && startY != -1) {
+            // Drag started
+            xDiff = startX - endX;
+            yDiff = startY - endY;
+        }
+
         startX = -1;
         startY = -1;
         mouseMoveStarted = false;
diff --git a/client/src/com/vaadin/client/ui/calendar/schedule/SimpleDayCell.java b/client/src/com/vaadin/client/ui/calendar/schedule/SimpleDayCell.java
index 3bf6930933..158241337b 100644
--- a/client/src/com/vaadin/client/ui/calendar/schedule/SimpleDayCell.java
+++ b/client/src/com/vaadin/client/ui/calendar/schedule/SimpleDayCell.java
@@ -392,8 +392,11 @@ public class SimpleDayCell extends FocusableFlowPanel implements
 
             int endX = event.getClientX();
             int endY = event.getClientY();
-            int xDiff = startX - endX;
-            int yDiff = startY - endY;
+            int xDiff = 0, yDiff = 0;
+            if (startX != -1 && startY != -1) {
+                xDiff = startX - endX;
+                yDiff = startY - endY;
+            }
             startX = -1;
             startY = -1;
             prevDayDiff = 0;