diff --git a/gui/builtinContextMenus/cargo.py b/gui/builtinContextMenus/cargo.py
index 672101c46..6eda67458 100644
--- a/gui/builtinContextMenus/cargo.py
+++ b/gui/builtinContextMenus/cargo.py
@@ -75,7 +75,7 @@ class CargoChanger(wx.Dialog):
         mainFrame = gui.mainFrame.MainFrame.getInstance()
         fitID = mainFrame.getActiveFit()
 
-        sFit.addCargo(fitID, self.cargo, int(self.input.GetLineText(0)))
+        sFit.addCargo(fitID, self.cargo.item.ID, int(self.input.GetLineText(0)), replace=True)
 
         wx.PostEvent(mainFrame, GE.FitChanged(fitID=fitID))
 
diff --git a/service/fit.py b/service/fit.py
index c3685685a..bc7e7bf56 100644
--- a/service/fit.py
+++ b/service/fit.py
@@ -478,7 +478,11 @@ class Fit(object):
             eos.db.commit()
             self.recalc(fit)
 
-    def addCargo(self, fitID, itemID, amount=1):
+    def addCargo(self, fitID, itemID, amount=1, replace = False):
+        '''Adds cargo via typeID of item. If replace = True, we replace amount with
+        given parameter, otherwise we increment
+        '''
+
         if fitID == None:
             return False
 
@@ -499,7 +503,10 @@ class Fit(object):
             cargo = eos.types.Cargo(item)
 
         fit.cargo.append(cargo)
-        cargo.amount += amount
+        if replace:
+            cargo.amount = amount
+        else:
+            cargo.amount += amount
 
         self.recalc(fit)
         eos.db.commit()