diff --git a/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj b/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
index 2caa41779b..88c872f078 100644
--- a/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
+++ b/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
@@ -593,6 +593,7 @@
     <Compile Include="Traits\World\ActorSpawnManager.cs" />
     <Compile Include="Traits\ActorSpawner.cs" />
     <Compile Include="UpdateRules\Rules\20180923\RemovedDemolishLocking.cs" />
+    <Compile Include="UpdateRules\Rules\20180923\RemoveNegativeDamageFullHealthCheck.cs" />
     <Compile Include="UpdateRules\Rules\20180923\RenameCrateActionNotification.cs" />
     <Compile Include="UpdateRules\Rules\20180923\CloakRequiresConditionToPause.cs" />
     <Compile Include="UpdateRules\Rules\20180923\MergeCaptureTraits.cs" />
diff --git a/OpenRA.Mods.Common/UpdateRules/Rules/20180923/RemoveNegativeDamageFullHealthCheck.cs b/OpenRA.Mods.Common/UpdateRules/Rules/20180923/RemoveNegativeDamageFullHealthCheck.cs
new file mode 100644
index 0000000000..8f0c7885ce
--- /dev/null
+++ b/OpenRA.Mods.Common/UpdateRules/Rules/20180923/RemoveNegativeDamageFullHealthCheck.cs
@@ -0,0 +1,70 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OpenRA.Mods.Common.UpdateRules.Rules
+{
+	public class RemoveNegativeDamageFullHealthCheck : UpdateRule
+	{
+		public override string Name { get { return "Negative damage weapons are now valid against full-health targets."; } }
+		public override string Description
+		{
+			get
+			{
+				return "Negative-damage weapons are no longer automatically invalid against targets that have full health.\n" +
+				       "Previous behaviour can be restored by enabling a Targetable trait using GrantConditionOnDamageState.\n" +
+				       "Affected weapons are listed so that conditions may be manually defined.";
+			}
+		}
+
+		static readonly string[] DamageWarheads =
+		{
+			"TargetDamage",
+			"SpreadDamage",
+			"HealthPercentageDamage"
+		};
+
+		readonly Dictionary<string, List<string>> locations = new Dictionary<string, List<string>>();
+
+		public override IEnumerable<string> AfterUpdate(ModData modData)
+		{
+			if (locations.Any())
+				yield return "The following weapons may now target actors that have full health. Review their\n" +
+					"target types and, if necessary, use GrantConditionOnDamageState to enable\n" +
+					"a conditional Targetable trait with the appropriate target type when damaged:\n" +
+					UpdateUtils.FormatMessageList(locations.Select(
+						kv => kv.Key + ":\n" + UpdateUtils.FormatMessageList(kv.Value)));
+
+			locations.Clear();
+		}
+
+		public override IEnumerable<string> UpdateWeaponNode(ModData modData, MiniYamlNode weaponNode)
+		{
+			var used = new List<string>();
+			foreach (var node in weaponNode.ChildrenMatching("Warhead"))
+			{
+				foreach (var warhead in DamageWarheads)
+					if (node.NodeValue<string>() == warhead && node.ChildrenMatching("Damage").Any(d => d.NodeValue<int>() < 0))
+						used.Add(node.Key);
+
+				if (used.Any())
+				{
+					var location = "{0} ({1})".F(weaponNode.Key, node.Location.Filename);
+					locations[location] = used;
+				}
+			}
+
+			yield break;
+		}
+	}
+}
diff --git a/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs b/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
index 6e95ac3d53..ca627cbd56 100644
--- a/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
+++ b/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
@@ -107,6 +107,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new CloakRequiresConditionToPause(),
 				new AddBotOrderManager(),
 				new AddHarvesterBotModule(),
+				new RemoveNegativeDamageFullHealthCheck(),
 			})
 		};
 
diff --git a/OpenRA.Mods.Common/Warheads/DamageWarhead.cs b/OpenRA.Mods.Common/Warheads/DamageWarhead.cs
index f4f6bbd4ee..b5923f750f 100644
--- a/OpenRA.Mods.Common/Warheads/DamageWarhead.cs
+++ b/OpenRA.Mods.Common/Warheads/DamageWarhead.cs
@@ -34,9 +34,6 @@ namespace OpenRA.Mods.Common.Warheads
 			if (!victim.Info.HasTraitInfo<IHealthInfo>())
 				return false;
 
-			if (Damage < 0 && victim.GetDamageState() == DamageState.Undamaged)
-				return false;
-
 			return base.IsValidAgainst(victim, firedBy);
 		}