diff --git a/OpenRA.Mods.Common/Scripting/Properties/ConditionProperties.cs b/OpenRA.Mods.Common/Scripting/Properties/ConditionProperties.cs
index 1e1df80305..46f4872fb4 100644
--- a/OpenRA.Mods.Common/Scripting/Properties/ConditionProperties.cs
+++ b/OpenRA.Mods.Common/Scripting/Properties/ConditionProperties.cs
@@ -36,7 +36,7 @@ namespace OpenRA.Mods.Common.Scripting
 			"If duration > 0 the condition will be automatically revoked after the defined number of ticks")]
 		public int GrantCondition(string condition, int duration = 0)
 		{
-			if (!conditionManager.AcceptsExternalCondition(Self, condition))
+			if (!conditionManager.AcceptsExternalCondition(Self, condition, duration > 0))
 				throw new InvalidDataException("Condition `{0}` has not been listed on an ExternalConditions trait".F(condition));
 
 			return conditionManager.GrantCondition(Self, condition, true, duration);
@@ -49,9 +49,9 @@ namespace OpenRA.Mods.Common.Scripting
 		}
 
 		[Desc("Check whether this actor accepts a specific external condition.")]
-		public bool AcceptsCondition(string condition)
+		public bool AcceptsCondition(string condition, bool timed = false)
 		{
-			return conditionManager.AcceptsExternalCondition(Self, condition);
+			return conditionManager.AcceptsExternalCondition(Self, condition, timed);
 		}
 
 		[Desc("Grant an upgrade to this actor. DEPRECATED! Will be removed.")]
diff --git a/OpenRA.Mods.Common/Traits/Conditions/ConditionManager.cs b/OpenRA.Mods.Common/Traits/Conditions/ConditionManager.cs
index 31e79fd5ec..875733a518 100644
--- a/OpenRA.Mods.Common/Traits/Conditions/ConditionManager.cs
+++ b/OpenRA.Mods.Common/Traits/Conditions/ConditionManager.cs
@@ -211,7 +211,7 @@ namespace OpenRA.Mods.Common.Traits
 		}
 
 		/// <summary>Returns true if the given external condition will have an effect on this actor.</summary>
-		public bool AcceptsExternalCondition(Actor self, string condition)
+		public bool AcceptsExternalCondition(Actor self, string condition, bool timed = false)
 		{
 			if (state == null)
 				throw new InvalidOperationException("AcceptsExternalCondition cannot be queried before the actor has been fully created.");
@@ -219,6 +219,10 @@ namespace OpenRA.Mods.Common.Traits
 			if (!externalConditions.Contains(condition))
 				return false;
 
+			// A timed condition can always replace an existing timed condition (resetting its duration)
+			if (timed && timers.ContainsKey(condition))
+				return true;
+
 			string[] sc;
 			if (stackedConditions.TryGetValue(condition, out sc))
 				return stackedTokens[condition].Count < sc.Length;
diff --git a/OpenRA.Mods.Common/Traits/Crates/GrantExternalConditionCrateAction.cs b/OpenRA.Mods.Common/Traits/Crates/GrantExternalConditionCrateAction.cs
index 3681aadfd2..0a9ea8a2bc 100644
--- a/OpenRA.Mods.Common/Traits/Crates/GrantExternalConditionCrateAction.cs
+++ b/OpenRA.Mods.Common/Traits/Crates/GrantExternalConditionCrateAction.cs
@@ -48,7 +48,7 @@ namespace OpenRA.Mods.Common.Traits
 		bool AcceptsCondition(Actor a)
 		{
 			var cm = a.TraitOrDefault<ConditionManager>();
-			return cm != null && cm.AcceptsExternalCondition(a, info.Condition);
+			return cm != null && cm.AcceptsExternalCondition(a, info.Condition, info.Duration > 0);
 		}
 
 		public override int GetSelectionShares(Actor collector)
diff --git a/OpenRA.Mods.Common/Traits/SupportPowers/GrantExternalConditionPower.cs b/OpenRA.Mods.Common/Traits/SupportPowers/GrantExternalConditionPower.cs
index f0eacb4541..2e00ebefc9 100644
--- a/OpenRA.Mods.Common/Traits/SupportPowers/GrantExternalConditionPower.cs
+++ b/OpenRA.Mods.Common/Traits/SupportPowers/GrantExternalConditionPower.cs
@@ -91,7 +91,7 @@ namespace OpenRA.Mods.Common.Traits
 					return false;
 
 				var cm = a.TraitOrDefault<ConditionManager>();
-				return cm != null && cm.AcceptsExternalCondition(a, info.Condition);
+				return cm != null && cm.AcceptsExternalCondition(a, info.Condition, info.Duration > 0);
 			});
 		}
 
diff --git a/OpenRA.Mods.Common/Warheads/GrantExternalConditionWarhead.cs b/OpenRA.Mods.Common/Warheads/GrantExternalConditionWarhead.cs
index be5f1ccd91..31884f8431 100644
--- a/OpenRA.Mods.Common/Warheads/GrantExternalConditionWarhead.cs
+++ b/OpenRA.Mods.Common/Warheads/GrantExternalConditionWarhead.cs
@@ -39,7 +39,7 @@ namespace OpenRA.Mods.Common.Warheads
 				var cm = a.TraitOrDefault<ConditionManager>();
 
 				// Condition token is ignored because we never revoke this condition.
-				if (cm != null && cm.AcceptsExternalCondition(a, Condition))
+				if (cm != null && cm.AcceptsExternalCondition(a, Condition, Duration > 0))
 					cm.GrantCondition(a, Condition, true, Duration);
 			}
 		}