diff --git a/app/js/shipyard/factory-ship.js b/app/js/shipyard/factory-ship.js
index a4d2a90e..c75f004e 100755
--- a/app/js/shipyard/factory-ship.js
+++ b/app/js/shipyard/factory-ship.js
@@ -164,11 +164,11 @@ angular.module('shipyard').factory('Ship', ['Components', 'calcShieldStrength',
   Ship.prototype.use = function(slot, id, component, preventUpdate) {
     if (slot.id != id) { // Selecting a different component
       // Slot is an internal slot, is not being emptied, and the selected component group/type must be of unique
-      if (slot.cat != 2 && component && _.includes(['sg', 'rf', 'fs'], component.grp)) {
+      if (slot.cat == 2 && component && _.includes(['sg', 'rf', 'fs'], component.grp)) {
         // Find another internal slot that already has this type/group installed
         var similarSlot = this.findInternalByGroup(component.grp);
         // If another slot has an installed component with of the same type
-        if (similarSlot && similarSlot !== slot) {
+        if (!preventUpdate && similarSlot && similarSlot !== slot) {
           this.updateStats(similarSlot, null, similarSlot.c, true);  // Update stats but don't trigger a global update
           similarSlot.id = similarSlot.c = null;  // Empty the slot
         }
diff --git a/package.json b/package.json
index 5bfde49a..6ee650a5 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "coriolis_shipyard",
-  "version": "0.13.2",
+  "version": "0.13.3",
   "repository": {
     "type": "git",
     "url": "https://github.com/cmmcleod/coriolis"
diff --git a/test/tests/test-factory-ship.js b/test/tests/test-factory-ship.js
index f4242270..03280c9a 100644
--- a/test/tests/test-factory-ship.js
+++ b/test/tests/test-factory-ship.js
@@ -1,10 +1,12 @@
 describe("Ship Factory", function() {
 
   var Ship;
+  var Components;
 
   beforeEach(module('shipyard'));
-  beforeEach(inject(['Ship', function (_Ship_) {
+  beforeEach(inject(['Ship', 'Components', function (_Ship_, _Components_) {
     Ship = _Ship_;
+    Components = _Components_;
   }]));
 
   it("can build all ships", function() {
@@ -32,39 +34,89 @@ describe("Ship Factory", function() {
   });
 
   it("resets and rebuilds properly", function() {
-      var id = 'cobra_mk_iii';
-      var cobra = DB.ships[id];
-      var shipA = new Ship(id, cobra.properties, cobra.slots);
-      var shipB = new Ship(id, cobra.properties, cobra.slots);
-      var testShip = new Ship(id, cobra.properties, cobra.slots);
+    var id = 'cobra_mk_iii';
+    var cobra = DB.ships[id];
+    var shipA = new Ship(id, cobra.properties, cobra.slots);
+    var shipB = new Ship(id, cobra.properties, cobra.slots);
+    var testShip = new Ship(id, cobra.properties, cobra.slots);
 
-      var buildA = cobra.defaults;
-      var buildB = {
-        common:['4A', '4A', '4A', '3D', '3A', '3A', '4C'],
-        hardpoints: ['0s', '0s', '2d', '2d', 0, '04'],
-        internal: ['45', '03', '2b', '2o', '27', '53']
-      };
+    var buildA = cobra.defaults;
+    var buildB = {
+      common:['4A', '4A', '4A', '3D', '3A', '3A', '4C'],
+      hardpoints: ['0s', '0s', '2d', '2d', 0, '04'],
+      internal: ['45', '03', '2b', '2o', '27', '53']
+    };
 
-      shipA.buildWith(buildA); // Build A
-      shipB.buildWith(buildB);// Build B
-      testShip.buildWith(buildA);
+    shipA.buildWith(buildA); // Build A
+    shipB.buildWith(buildB);// Build B
+    testShip.buildWith(buildA);
 
-      for(var p in testShip) {
-        expect(testShip[p]).toEqual(shipA[p], p + ' does not match');
-      }
+    for(var p in testShip) {
+      expect(testShip[p]).toEqual(shipA[p], p + ' does not match');
+    }
 
-      testShip.buildWith(buildB);
+    testShip.buildWith(buildB);
 
-      for(var p in testShip) {
-        expect(testShip[p]).toEqual(shipB[p], p + ' does not match');
-      }
+    for(var p in testShip) {
+      expect(testShip[p]).toEqual(shipB[p], p + ' does not match');
+    }
 
-      testShip.buildWith(buildA);
+    testShip.buildWith(buildA);
 
-      for(var p in testShip) {
-        expect(testShip[p]).toEqual(shipA[p], p + ' does not match');
-      }
+    for(var p in testShip) {
+      expect(testShip[p]).toEqual(shipA[p], p + ' does not match');
+    }
+  });
+
+  it("enforces a single shield generator", function() {
+    var id = 'anaconda';
+    var anacondaData = DB.ships[id];
+    var anaconda = new Ship(id, anacondaData.properties, anacondaData.slots);
+    anaconda.buildWith(anacondaData.defaults);
+
+    expect(anaconda.internal[2].c.grp).toEqual('sg', 'Anaconda default shield generator slot');
+
+    anaconda.use(anaconda.internal[1], '4j', Components.internal('4j'));  // 6E Shield Generator
+
+    expect(anaconda.internal[2].c).toEqual(null, 'Anaconda default shield generator slot is empty');
+    expect(anaconda.internal[2].id).toEqual(null, 'Anaconda default shield generator slot id is null');
+    expect(anaconda.internal[1].id).toEqual('4j', 'Slot 1 should have SG 4j in it');
+    expect(anaconda.internal[1].c.grp).toEqual('sg','Slot 1 should have SG 4j in it');
 
   });
 
-});
\ No newline at end of file
+  it("enforces a single shield fuel scoop", function() {
+    var id = 'anaconda';
+    var anacondaData = DB.ships[id];
+    var anaconda = new Ship(id, anacondaData.properties, anacondaData.slots);
+    anaconda.buildWith(anacondaData.defaults);
+
+    anaconda.use(anaconda.internal[4], '32', Components.internal('32')); // 4A Fuel Scoop
+    expect(anaconda.internal[4].c.grp).toEqual('fs', 'Anaconda fuel scoop slot');
+
+    anaconda.use(anaconda.internal[3], '32', Components.internal('32'));
+
+    expect(anaconda.internal[4].c).toEqual(null, 'Anaconda original fuel scoop slot is empty');
+    expect(anaconda.internal[4].id).toEqual(null, 'Anaconda original fuel scoop slot id is null');
+    expect(anaconda.internal[3].id).toEqual('32', 'Slot 1 should have FS 32 in it');
+    expect(anaconda.internal[3].c.grp).toEqual('fs','Slot 1 should have FS 32 in it');
+  });
+
+  it("enforces a single refinery", function() {
+    var id = 'anaconda';
+    var anacondaData = DB.ships[id];
+    var anaconda = new Ship(id, anacondaData.properties, anacondaData.slots);
+    anaconda.buildWith(anacondaData.defaults);
+
+    anaconda.use(anaconda.internal[4], '23', Components.internal('23')); // 4E Refinery
+    expect(anaconda.internal[4].c.grp).toEqual('rf', 'Anaconda refinery slot');
+
+    anaconda.use(anaconda.internal[3], '23', Components.internal('23'));
+
+    expect(anaconda.internal[4].c).toEqual(null, 'Anaconda original refinery slot is empty');
+    expect(anaconda.internal[4].id).toEqual(null, 'Anaconda original refinery slot id is null');
+    expect(anaconda.internal[3].id).toEqual('23', 'Slot 1 should have RF 23 in it');
+    expect(anaconda.internal[3].c.grp).toEqual('rf','Slot 1 should have RF 23 in it');
+  });
+
+});