diff --git a/OpenRa.Game/Exts.cs b/OpenRa.Game/Exts.cs
index b66ad80010..cc04e81a91 100644
--- a/OpenRa.Game/Exts.cs
+++ b/OpenRa.Game/Exts.cs
@@ -22,5 +22,10 @@ namespace OpenRa.Game
 			// this is probably a shockingly-slow way to do this, but it's concise.
 			return xs.Except(ys).Concat(ys.Except(xs));
 		}
+
+		public static float Product(this IEnumerable<float> xs)
+		{
+			return xs.Aggregate((a, x) => a * x);
+		}
 	}
 }
diff --git a/OpenRa.Game/Traits/Activities/Move.cs b/OpenRa.Game/Traits/Activities/Move.cs
index 4392571a68..c63702b180 100755
--- a/OpenRa.Game/Traits/Activities/Move.cs
+++ b/OpenRa.Game/Traits/Activities/Move.cs
@@ -168,11 +168,7 @@ namespace OpenRa.Game.Traits.Activities
 				var oldFraction = moveFraction;
 				var oldTotal = moveFractionTotal;
 
-				var actualSpeed = (int)self.traits.WithInterface<ISpeedModifier>().Aggregate(
-					(float)(self.Info as MobileInfo).Speed,
-					(a, t) => t.GetSpeedModifier() * a);
-
-				moveFraction += actualSpeed;
+				moveFraction += (int)Util.GetEffectiveSpeed(self);
 				UpdateCenterLocation( self, mobile );
 				if( moveFraction >= moveFractionTotal )
 				{
diff --git a/OpenRa.Game/Traits/Helicopter.cs b/OpenRa.Game/Traits/Helicopter.cs
index 5a958f16ee..2b16d5432d 100644
--- a/OpenRa.Game/Traits/Helicopter.cs
+++ b/OpenRa.Game/Traits/Helicopter.cs
@@ -48,12 +48,7 @@ namespace OpenRa.Game.Traits
 				Util.TickFacing(ref unit.Facing, desiredFacing,
 					self.Info.ROT);
 
-				var actualSpeed = self.traits.WithInterface<ISpeedModifier>().Aggregate(
-					(float)(self.Info as MobileInfo).Speed,
-					(a, t) => t.GetSpeedModifier() * a);
-
-				// .6f going the wrong way; .8f going sideways, 1f going forward.
-				var rawSpeed = .2f * actualSpeed;
+				var rawSpeed = .2f * Util.GetEffectiveSpeed(self);
 				var angle = (unit.Facing - desiredFacing) / 128f * Math.PI;
 				var scale = .4f + .6f * (float)Math.Cos(angle);
 
diff --git a/OpenRa.Game/Traits/Mobile.cs b/OpenRa.Game/Traits/Mobile.cs
index 8b242b842c..8e8908f13f 100644
--- a/OpenRa.Game/Traits/Mobile.cs
+++ b/OpenRa.Game/Traits/Mobile.cs
@@ -32,6 +32,7 @@ namespace OpenRa.Game.Traits
 		{
 			if (mi.Button == MouseButton.Left) return null;
 			if (underCursor != null) return null;
+			if (Util.GetEffectiveSpeed(self) == 0) return null;		/* allow disabling move orders from modifiers */
 			if (xy == toCell) return null;
 			return Order.Move(self, xy);
 		}
diff --git a/OpenRa.Game/Traits/Util.cs b/OpenRa.Game/Traits/Util.cs
index 818688e05f..e3a77389db 100755
--- a/OpenRa.Game/Traits/Util.cs
+++ b/OpenRa.Game/Traits/Util.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using OpenRa.Game.Graphics;
+using OpenRa.Game.GameRules;
 
 namespace OpenRa.Game.Traits
 {
@@ -124,5 +125,17 @@ namespace OpenRa.Game.Traits
 			var loc = location - 0.5f * s.size;
 			return Tuple.New(s, loc.Round(), 8);
 		}
+
+		public static float GetEffectiveSpeed(Actor self)
+		{
+			var mi = self.Info as MobileInfo;
+			if (mi == null) return 0f;
+
+			var modifier = self.traits
+				.WithInterface<ISpeedModifier>()
+				.Select(t => t.GetSpeedModifier())
+				.Product();
+			return mi.Speed * modifier;
+		}
 	}
 }