Index: binaries/data/mods/public/gui/session/input.js
===================================================================
--- binaries/data/mods/public/gui/session/input.js
+++ binaries/data/mods/public/gui/session/input.js
@@ -1348,7 +1348,7 @@
 	return entitiesToCheck.filter(entity => {
 		let state = GetEntityState(entity);
 		return state && state.production && state.production.entities.length &&
-			state.production.entities.indexOf(trainEntType) != -1;
+			state.production.entities.indexOf(trainEntType) != -1 && (!state.upgrade || !state.upgrade.upgrading);
 	});
 }
 
Index: binaries/data/mods/public/gui/session/selection_panels.js
===================================================================
--- binaries/data/mods/public/gui/session/selection_panels.js
+++ binaries/data/mods/public/gui/session/selection_panels.js
@@ -798,6 +798,14 @@
 			else
 				button.enabled = controlsPlayer(data.player);
 
+			if (data.unitEntStates.every(state => state.upgrade && state.upgrade.isUpgrading))
+			{
+				button.enabled = false;
+				modifier += "color:0 0 0 127:grayscale:";
+				button.tooltip += "\n" + coloredText(translate("Cannot research while upgrading."), "red");
+
+			}
+
 			if (template.icon)
 				icon.sprite = modifier + "stretched:session/portraits/" + template.icon;
 
@@ -1011,6 +1019,13 @@
 				modifier = resourcesToAlphaMask(neededResources) + ":";
 		}
 
+		if (data.unitEntStates.every(state => state.upgrade && state.upgrade.isUpgrading))
+		{
+			data.button.enabled = false;
+			modifier = "color:0 0 0 127:grayscale:";
+			data.button.tooltip += "\n" + coloredText(translate("Cannot train while upgrading."), "red");
+		}
+
 		if (template.icon)
 			data.icon.sprite = modifier + "stretched:session/portraits/" + template.icon;
 
@@ -1114,6 +1129,13 @@
 				modifier = resourcesToAlphaMask(neededResources) + ":";
 			}
 
+		if (data.unitEntStates.every(state => state.production && state.production.queue && state.production.queue.length))
+		{
+			data.button.enabled = false;
+			modifier = "color:0 0 0 127:grayscale:";
+			data.button.tooltip += "\n" + coloredText(translate("Cannot upgrade while training or researching"), "red");
+		}
+
 		data.icon.sprite = modifier + "stretched:session/" +
 			(data.item.icon || "portraits/" + template.icon);
 
Index: binaries/data/mods/public/simulation/components/GuiInterface.js
===================================================================
--- binaries/data/mods/public/simulation/components/GuiInterface.js
+++ binaries/data/mods/public/simulation/components/GuiInterface.js
@@ -308,7 +308,8 @@
 		ret.upgrade = {
 			"upgrades": cmpUpgrade.GetUpgrades(),
 			"progress": cmpUpgrade.GetProgress(),
-			"template": cmpUpgrade.GetUpgradingTo()
+			"template": cmpUpgrade.GetUpgradingTo(),
+			"isUpgrading": cmpUpgrade.IsUpgrading()
 		};
 
 	let cmpStatusEffects = Engine.QueryInterface(ent, IID_StatusEffectsReceiver);
Index: binaries/data/mods/public/simulation/components/ProductionQueue.js
===================================================================
--- binaries/data/mods/public/simulation/components/ProductionQueue.js
+++ binaries/data/mods/public/simulation/components/ProductionQueue.js
@@ -324,6 +324,21 @@
 	// to be possible to add a batch (based on resource costs and length limits).
 	let cmpPlayer = QueryOwnerInterface(this.entity);
 
+	if (!this.queue.length)
+	{
+		let cmpUpgrade = Engine.QueryInterface(this.entity, IID_Upgrade);
+		if (cmpUpgrade && cmpUpgrade.IsUpgrading())
+		{
+			let cmpGUIInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+			cmpGUIInterface.PushNotification({
+			    "players": [cmpPlayer.GetPlayerID()],
+			    "message": markForTranslation("Entity is being upgraded. Cannot start production."),
+			    "translateMessage": true
+			});
+			return;
+		}
+	}
+
 	if (this.queue.length < this.MaxQueueSize)
 	{
 
@@ -947,6 +962,11 @@
 		Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface).SetSelectionDirty(cmpPlayer.GetPlayerID());
 };
 
+ProductionQueue.prototype.HasQueuedProduction = function()
+{
+	return this.queue.length > 0;
+}
+
 ProductionQueue.prototype.OnDisabledTemplatesChanged = function(msg)
 {
 	// If the disabled templates of the player is changed,
Index: binaries/data/mods/public/simulation/components/Upgrade.js
===================================================================
--- binaries/data/mods/public/simulation/components/Upgrade.js
+++ binaries/data/mods/public/simulation/components/Upgrade.js
@@ -228,6 +228,17 @@
 		return false;
 
 	let cmpPlayer = QueryOwnerInterface(this.entity, IID_Player);
+	let cmpProductionQueue = Engine.QueryInterface(this.entity, IID_ProductionQueue);
+	if (cmpProductionQueue && cmpProductionQueue.HasQueuedProduction())
+	{
+		let cmpGUIInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
+		cmpGUIInterface.PushNotification({
+		    "players": [cmpPlayer.GetPlayerID()],
+		    "message": markForTranslation("Entity is producing. Cannot start upgrading."),
+		    "translateMessage": true
+		});
+		return false;
+	}
 
 	this.expendedResources = this.GetResourceCosts(template);
 	if (!cmpPlayer.TrySubtractResources(this.expendedResources))
Index: binaries/data/mods/public/simulation/components/tests/test_ProductionQueue.js
===================================================================
--- binaries/data/mods/public/simulation/components/tests/test_ProductionQueue.js
+++ binaries/data/mods/public/simulation/components/tests/test_ProductionQueue.js
@@ -9,6 +9,7 @@
 Engine.LoadComponentScript("interfaces/Timer.js");
 Engine.LoadComponentScript("interfaces/TrainingRestrictions.js");
 Engine.LoadComponentScript("interfaces/Trigger.js");
+Engine.LoadComponentScript("interfaces/Upgrade.js");
 Engine.LoadComponentScript("EntityLimits.js");
 
 Engine.RegisterGlobal("Resources", {
@@ -71,6 +72,10 @@
 		"GetCiv": () => "iber"
 	});
 
+	AddMock(productionQueueId, IID_Upgrade, {
+		"IsUpgrading": () => false
+	});
+
 	cmpProductionQueue.CalculateEntitiesMap();
 	TS_ASSERT_UNEVAL_EQUALS(
 		cmpProductionQueue.GetEntitiesList(),
@@ -273,6 +278,10 @@
 		"PickSpawnPoint": () => ({ "x": -1, "y": -1, "z": -1 })
 	});
 
+	AddMock(testEntity, IID_Upgrade, {
+		"IsUpgrading": () => false
+	});
+
 	cmpProdQueue.AddBatch("some_template", "unit", 3);
 	Engine.QueryInterface(testEntity, IID_ProductionQueue).ProgressTimeout();
 
Index: binaries/data/mods/public/simulation/components/tests/test_UpgradeModification.js
===================================================================
--- binaries/data/mods/public/simulation/components/tests/test_UpgradeModification.js
+++ binaries/data/mods/public/simulation/components/tests/test_UpgradeModification.js
@@ -13,6 +13,7 @@
 		return "<interleave>" + schema + "</interleave>";
 	}
 };
+Engine.LoadComponentScript("interfaces/ProductionQueue.js");
 Engine.LoadComponentScript("interfaces/ModifiersManager.js"); // Provides `IID_ModifiersManager`, used below.
 Engine.LoadComponentScript("interfaces/Timer.js"); // Provides `IID_Timer`, used below.
 
@@ -120,6 +121,9 @@
 AddMock(20, IID_Identity, {
 	"GetCiv": () => civCode // Called in components/Upgrade.js::init().
 });
+AddMock(20, IID_ProductionQueue, {
+	"HasQueuedProduction": () => false
+})
 let cmpUpgrade = ConstructComponent(20, "Upgrade", template.Upgrade);
 cmpUpgrade.owner = playerID;