diff --git a/binaries/data/mods/public/simulation/components/Builder.js b/binaries/data/mods/public/simulation/components/Builder.js
index 0b07dacbfb..6245ab76f9 100644
--- a/binaries/data/mods/public/simulation/components/Builder.js
+++ b/binaries/data/mods/public/simulation/components/Builder.js
@@ -75,7 +75,7 @@ Builder.prototype.CanRepair = function(target)
 {
 	let cmpFoundation = QueryMiragedInterface(target, IID_Foundation);
 	let cmpRepairable = QueryMiragedInterface(target, IID_Repairable);
-	if (!cmpFoundation && !cmpRepairable)
+	if (!cmpFoundation && (!cmpRepairable || !cmpRepairable.IsRepairable()))
 		return false;
 
 	let cmpOwnership = Engine.QueryInterface(this.entity, IID_Ownership);
diff --git a/binaries/data/mods/public/simulation/components/Health.js b/binaries/data/mods/public/simulation/components/Health.js
index bd0ed41e21..ca37e7f7ed 100644
--- a/binaries/data/mods/public/simulation/components/Health.js
+++ b/binaries/data/mods/public/simulation/components/Health.js
@@ -109,7 +109,8 @@ Health.prototype.SetHitpoints = function(value)
 
 Health.prototype.IsRepairable = function()
 {
-	return Engine.QueryInterface(this.entity, IID_Repairable) != null;
+	let cmpRepairable = Engine.QueryInterface(this.entity, IID_Repairable);
+	return cmpRepairable && cmpRepairable.IsRepairable();
 };
 
 Health.prototype.IsUnhealable = function()
diff --git a/binaries/data/mods/public/simulation/components/Repairable.js b/binaries/data/mods/public/simulation/components/Repairable.js
index 35cc6c8a14..b2f7f5e5bf 100644
--- a/binaries/data/mods/public/simulation/components/Repairable.js
+++ b/binaries/data/mods/public/simulation/components/Repairable.js
@@ -33,6 +33,19 @@ Repairable.prototype.GetBuildProgress = function()
 	return hitpoints / maxHitpoints;
 };
 
+/**
+ * @return whether this entity can be repaired (this does not account for health).
+ */
+Repairable.prototype.IsRepairable = function()
+{
+	return !this.unrepairable;
+};
+
+Repairable.prototype.SetRepairability = function(repairable)
+{
+	this.unrepairable = !repairable;
+};
+
 /**
  * Returns the current builders.
  *
diff --git a/binaries/data/mods/public/simulation/components/tests/test_Builder.js b/binaries/data/mods/public/simulation/components/tests/test_Builder.js
index 613a480ea0..0da3ed5b52 100644
--- a/binaries/data/mods/public/simulation/components/tests/test_Builder.js
+++ b/binaries/data/mods/public/simulation/components/tests/test_Builder.js
@@ -1,10 +1,14 @@
 Engine.LoadHelperScript("Player.js");
 Engine.LoadComponentScript("interfaces/Builder.js");
+Engine.LoadComponentScript("interfaces/Cost.js");
 Engine.LoadComponentScript("interfaces/Foundation.js");
+Engine.LoadComponentScript("interfaces/Health.js");
 Engine.LoadComponentScript("interfaces/Repairable.js");
 Engine.LoadComponentScript("interfaces/Timer.js");
 Engine.LoadComponentScript("interfaces/UnitAI.js");
 Engine.LoadComponentScript("Builder.js");
+Engine.LoadComponentScript("Health.js");
+Engine.LoadComponentScript("Repairable.js");
 Engine.LoadComponentScript("Timer.js");
 
 const builderId = 6;
@@ -22,99 +26,165 @@ AddMock(SYSTEM_ENTITY, IID_TemplateManager, {
 
 Engine.RegisterGlobal("ApplyValueModificationsToEntity", (prop, oVal, ent) => oVal);
 
+function testEntitiesList()
+{
+	let cmpBuilder = ConstructComponent(builderId, "Builder", {
+		"Rate": "1.0",
+		"Entities": { "_string": "structures/{civ}/barracks structures/{civ}/civil_centre structures/{native}/house" }
+	});
 
-let cmpBuilder = ConstructComponent(builderId, "Builder", {
-	"Rate": "1.0",
-	"Entities": { "_string": "structures/{civ}/barracks structures/{civ}/civil_centre structures/{native}/house" }
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), []);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), []);
+	AddMock(SYSTEM_ENTITY, IID_PlayerManager, {
+		"GetPlayerByID": id => playerEntityID
+	});
 
-AddMock(SYSTEM_ENTITY, IID_PlayerManager, {
-	"GetPlayerByID": id => playerEntityID
-});
+	AddMock(playerEntityID, IID_Player, {
+		"GetCiv": () => "iber",
+		"GetDisabledTemplates": () => ({}),
+		"GetPlayerID": () => playerId
+	});
 
-AddMock(playerEntityID, IID_Player, {
-	"GetCiv": () => "iber",
-	"GetDisabledTemplates": () => ({}),
-	"GetPlayerID": () => playerId
-});
+	AddMock(builderId, IID_Ownership, {
+		"GetOwner": () => playerId
+	});
 
-AddMock(builderId, IID_Ownership, {
-	"GetOwner": () => playerId
-});
+	AddMock(builderId, IID_Identity, {
+		"GetCiv": () => "iber"
+	});
 
-AddMock(builderId, IID_Identity, {
-	"GetCiv": () => "iber"
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/barracks", "structures/iber/civil_centre", "structures/iber/house"]);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/barracks", "structures/iber/civil_centre", "structures/iber/house"]);
+	AddMock(SYSTEM_ENTITY, IID_TemplateManager, {
+		"TemplateExists": name => name == "structures/iber/civil_centre"
+	});
 
-AddMock(SYSTEM_ENTITY, IID_TemplateManager, {
-	"TemplateExists": name => name == "structures/iber/civil_centre"
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/civil_centre"]);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/civil_centre"]);
+	AddMock(SYSTEM_ENTITY, IID_TemplateManager, {
+		"TemplateExists": () => true
+	});
 
-AddMock(SYSTEM_ENTITY, IID_TemplateManager, {
-	"TemplateExists": () => true
-});
+	AddMock(playerEntityID, IID_Player, {
+		"GetCiv": () => "iber",
+		"GetDisabledTemplates": () => ({ "structures/athen/barracks": true }),
+		"GetPlayerID": () => playerId
+	});
 
-AddMock(playerEntityID, IID_Player, {
-	"GetCiv": () => "iber",
-	"GetDisabledTemplates": () => ({ "structures/athen/barracks": true }),
-	"GetPlayerID": () => playerId
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/barracks", "structures/iber/civil_centre", "structures/iber/house"]);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/barracks", "structures/iber/civil_centre", "structures/iber/house"]);
+	AddMock(playerEntityID, IID_Player, {
+		"GetCiv": () => "iber",
+		"GetDisabledTemplates": () => ({ "structures/iber/barracks": true }),
+		"GetPlayerID": () => playerId
+	});
 
-AddMock(playerEntityID, IID_Player, {
-	"GetCiv": () => "iber",
-	"GetDisabledTemplates": () => ({ "structures/iber/barracks": true }),
-	"GetPlayerID": () => playerId
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/civil_centre", "structures/iber/house"]);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/iber/civil_centre", "structures/iber/house"]);
+	AddMock(playerEntityID, IID_Player, {
+		"GetCiv": () => "athen",
+		"GetDisabledTemplates": () => ({ "structures/athen/barracks": true }),
+		"GetPlayerID": () => playerId
+	});
 
-AddMock(playerEntityID, IID_Player, {
-	"GetCiv": () => "athen",
-	"GetDisabledTemplates": () => ({ "structures/athen/barracks": true }),
-	"GetPlayerID": () => playerId
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/athen/civil_centre", "structures/iber/house"]);
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetEntitiesList(), ["structures/athen/civil_centre", "structures/iber/house"]);
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetRange(), { "max": 2, "min": 0 });
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetRange(), { "max": 2, "min": 0 });
+	AddMock(builderId, IID_Obstruction, {
+		"GetSize": () => 1
+	});
 
-AddMock(builderId, IID_Obstruction, {
-	"GetSize": () => 1
-});
+	TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetRange(), { "max": 3, "min": 0 });
+}
+testEntitiesList();
 
-TS_ASSERT_UNEVAL_EQUALS(cmpBuilder.GetRange(), { "max": 3, "min": 0 });
+function testBuildingFoundation()
+{
+	let cmpBuilder = ConstructComponent(builderId, "Builder", {
+		"Rate": "1.0",
+		"Entities": { "_string": "" }
+	});
 
-// Test repairing.
-AddMock(playerEntityID, IID_Player, {
-	"IsAlly": (p) => p == playerId
-});
+	AddMock(playerEntityID, IID_Player, {
+		"IsAlly": (p) => p == playerId
+	});
 
-AddMock(target, IID_Ownership, {
-	"GetOwner": () => playerId
-});
+	AddMock(target, IID_Ownership, {
+		"GetOwner": () => playerId
+	});
 
-let increased = false;
-AddMock(target, IID_Foundation, {
-	"Build": (entity, amount) => {
-		increased = true;
-		TS_ASSERT_EQUALS(amount, 1);
-	},
-	"AddBuilder": () => {}
-});
+	let increased = false;
+	AddMock(target, IID_Foundation, {
+		"Build": (entity, amount) => {
+			increased = true;
+			TS_ASSERT_EQUALS(amount, 1);
+		},
+		"AddBuilder": () => {}
+	});
 
-let cmpTimer = ConstructComponent(SYSTEM_ENTITY, "Timer");
+	let cmpTimer = ConstructComponent(SYSTEM_ENTITY, "Timer");
 
-TS_ASSERT(cmpBuilder.StartRepairing(target));
-cmpTimer.OnUpdate({ "turnLength": 1 });
-TS_ASSERT(increased);
-increased = false;
-cmpTimer.OnUpdate({ "turnLength": 2 });
-TS_ASSERT(increased);
+	TS_ASSERT(cmpBuilder.StartRepairing(target));
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT(increased);
+	increased = false;
+	cmpTimer.OnUpdate({ "turnLength": 2 });
+	TS_ASSERT(increased);
+}
+testBuildingFoundation();
+
+function testRepairing()
+{
+	AddMock(playerEntityID, IID_Player, {
+		"IsAlly": (p) => p == playerId
+	});
+
+	let cmpBuilder = ConstructComponent(builderId, "Builder", {
+		"Rate": "1.0",
+		"Entities": { "_string": "" }
+	});
+
+	AddMock(target, IID_Ownership, {
+		"GetOwner": () => playerId
+	});
+
+	AddMock(target, IID_Cost, {
+		"GetBuildTime": () => 100
+	});
+
+	let cmpTargetHealth = ConstructComponent(target, "Health", {
+		"Max": 100,
+		"RegenRate": 0,
+		"IdleRegenRate": 0,
+		"DeathType": "vanish",
+		"Unhealable": false
+	});
+
+	cmpTargetHealth.SetHitpoints(50);
+
+	DeleteMock(target, IID_Foundation);
+	let cmpTargetRepairable = ConstructComponent(target, "Repairable", {
+		"RepairTimeRatio": 1,
+	});
+
+	let cmpTimer = ConstructComponent(SYSTEM_ENTITY, "Timer");
+
+	TS_ASSERT(cmpTargetRepairable.IsRepairable());
+	TS_ASSERT(cmpBuilder.StartRepairing(target));
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpTargetHealth.GetHitpoints(), 51);
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpTargetHealth.GetHitpoints(), 52);
+	cmpTargetRepairable.SetRepairability(false);
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpTargetHealth.GetHitpoints(), 52);
+	cmpTargetRepairable.SetRepairability(true);
+	// Check that we indeed stopped - shouldn't restart on its own.
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpTargetHealth.GetHitpoints(), 52);
+	TS_ASSERT(cmpBuilder.StartRepairing(target));
+	cmpTimer.OnUpdate({ "turnLength": 1 });
+	TS_ASSERT_EQUALS(cmpTargetHealth.GetHitpoints(), 53);
+}
+testRepairing();