diff --git a/eos/effectHandlerHelpers.py b/eos/effectHandlerHelpers.py
index 446273a45..3cba3e40f 100644
--- a/eos/effectHandlerHelpers.py
+++ b/eos/effectHandlerHelpers.py
@@ -197,14 +197,20 @@ class HandledImplantBoosterList(HandledList):
             self.remove(thing)
             return
 
+        self.makeRoom(thing)
+        HandledList.append(self, thing)
+
+    def makeRoom(self, thing):
         # if needed, remove booster that was occupying slot
         oldObj = next((m for m in self if m.slot == thing.slot), None)
         if oldObj:
-            pyfalog.info("Slot {0} occupied with {1}, replacing with {2}", thing.slot, oldObj.item.name, thing.item.name)
+            pyfalog.info("Slot {0} occupied with {1}, replacing with {2}", thing.slot, oldObj.item.name,
+                         thing.item.name)
+            itemID = oldObj.itemID
             oldObj.itemID = 0  # hack to remove from DB. See GH issue #324
             self.remove(oldObj)
-
-        HandledList.append(self, thing)
+            return itemID
+        return None
 
 
 class HandledSsoCharacterList(list):
diff --git a/gui/builtinAdditionPanes/boosterView.py b/gui/builtinAdditionPanes/boosterView.py
index ef9c88f2d..48b3ed36d 100644
--- a/gui/builtinAdditionPanes/boosterView.py
+++ b/gui/builtinAdditionPanes/boosterView.py
@@ -148,7 +148,7 @@ class BoosterView(d.Display):
 
     def removeBooster(self, booster):
         fitID = self.mainFrame.getActiveFit()
-        self.mainFrame.command.Submit(cmd.GuiRemoveImplantCommand(fitID, self.origional.index(booster)))
+        self.mainFrame.command.Submit(cmd.GuiRemoveBoosterCommand(fitID, self.origional.index(booster)))
 
     def click(self, event):
         event.Skip()
diff --git a/gui/fitCommands/calc/fitAddBooster.py b/gui/fitCommands/calc/fitAddBooster.py
index 356a742da..61f4f5b49 100644
--- a/gui/fitCommands/calc/fitAddBooster.py
+++ b/gui/fitCommands/calc/fitAddBooster.py
@@ -19,7 +19,7 @@ class FitAddBoosterCommand(wx.Command):
         self.fitID = fitID
         self.itemID = itemID
         self.new_index = None
-
+        self.old_item = None
     def Do(self):
         pyfalog.debug("Adding booster ({0}) to fit ID: {1}", self.itemID, self.fitID)
 
@@ -31,11 +31,19 @@ class FitAddBoosterCommand(wx.Command):
             pyfalog.warning("Invalid item: {0}", self.itemID)
             return False
 
+        self.old_item = fit.boosters.makeRoom(booster)
+
         fit.boosters.append(booster)
         self.new_index = fit.boosters.index(booster)
         return True
 
     def Undo(self):
+        if self.old_item:
+            # If we had an item in the slot previously, add it back.
+            cmd = FitAddBoosterCommand(self.fitID, self.old_item)
+            cmd.Do()
+            return True
+
         from .fitRemoveBooster import FitRemoveBoosterCommand  # Avoid circular import
         cmd = FitRemoveBoosterCommand(self.fitID, self.new_index)
         cmd.Do()
diff --git a/gui/fitCommands/calc/fitAddImplant.py b/gui/fitCommands/calc/fitAddImplant.py
index 91bc5be61..b65b53e69 100644
--- a/gui/fitCommands/calc/fitAddImplant.py
+++ b/gui/fitCommands/calc/fitAddImplant.py
@@ -18,6 +18,7 @@ class FitAddImplantCommand(wx.Command):
         wx.Command.__init__(self, True, "Cargo add")
         self.fitID = fitID
         self.itemID = itemID
+        self.old_item = None
 
     def Do(self):
         pyfalog.debug("Adding implant to fit ({0}) for item ID: {1}", self.fitID, self.itemID)
@@ -30,11 +31,18 @@ class FitAddImplantCommand(wx.Command):
             pyfalog.warning("Invalid item: {0}", self.itemID)
             return False
 
+        self.old_item = fit.implants.makeRoom(implant)
         fit.implants.append(implant)
         self.new_index = fit.implants.index(implant)
         return True
 
     def Undo(self):
+        if self.old_item:
+            # If we had an item in the slot previously, add it back.
+            cmd = FitAddImplantCommand(self.fitID, self.old_item)
+            cmd.Do()
+            return True
+
         from .fitRemoveImplant import FitRemoveImplantCommand  # Avoid circular import
         cmd = FitRemoveImplantCommand(self.fitID, self.new_index)
         cmd.Do()
diff --git a/gui/fitCommands/guiAddBooster.py b/gui/fitCommands/guiAddBooster.py
index 392ce3034..3dc423cf6 100644
--- a/gui/fitCommands/guiAddBooster.py
+++ b/gui/fitCommands/guiAddBooster.py
@@ -17,6 +17,7 @@ class GuiAddBoosterCommand(wx.Command):
 
     def Do(self):
         if self.internal_history.Submit(self.cmd):
+            self.sFit.recalc(self.fitID)
             wx.PostEvent(self.mainFrame, GE.FitChanged(fitID=self.fitID))
             return True
         return False
@@ -24,6 +25,7 @@ class GuiAddBoosterCommand(wx.Command):
     def Undo(self):
         for x in self.internal_history.Commands:
             self.internal_history.Undo()
+        self.sFit.recalc(self.fitID)
         wx.PostEvent(self.mainFrame, GE.FitChanged(fitID=self.fitID))
         return True
 
diff --git a/gui/fitCommands/guiRemoveBooster.py b/gui/fitCommands/guiRemoveBooster.py
index 92578b0b8..2155ab120 100644
--- a/gui/fitCommands/guiRemoveBooster.py
+++ b/gui/fitCommands/guiRemoveBooster.py
@@ -17,6 +17,7 @@ class GuiRemoveBoosterCommand(wx.Command):
 
     def Do(self):
         if self.internal_history.Submit(self.cmd):
+            self.sFit.recalc(self.fitID)
             wx.PostEvent(self.mainFrame, GE.FitChanged(fitID=self.fitID))
             return True
         return False
@@ -24,6 +25,7 @@ class GuiRemoveBoosterCommand(wx.Command):
     def Undo(self):
         for x in self.internal_history.Commands:
             self.internal_history.Undo()
+        self.sFit.recalc(self.fitID)
         wx.PostEvent(self.mainFrame, GE.FitChanged(fitID=self.fitID))
         return True