diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index cd78d4d9d0..19dc7f7d10 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,6 @@
 December 12, 2009
+- Added a DMG_NO_FACTOR flag for P_DamageMobj(). A_KillChildren, A_KillMaster,
+  and A_KillSiblings now use it.
 - Added a damage type parameter to A_KillChildren, A_KillMaster, and
   A_KillSiblings. 
 
diff --git a/src/p_interaction.cpp b/src/p_interaction.cpp
index 3c8f715f5e..003e0077ee 100644
--- a/src/p_interaction.cpp
+++ b/src/p_interaction.cpp
@@ -1000,21 +1000,24 @@ void P_DamageMobj (AActor *target, AActor *inflictor, AActor *source, int damage
 				return;
 		}
 
-		DmgFactors * df = target->GetClass()->ActorInfo->DamageFactors;
-		if (df != NULL)
+		if (!(flags & DMG_NO_FACTOR))
 		{
-			fixed_t * pdf = df->CheckKey(mod);
-			if (pdf== NULL && mod != NAME_None) pdf = df->CheckKey(NAME_None);
-			if (pdf != NULL)
+			DmgFactors *df = target->GetClass()->ActorInfo->DamageFactors;
+			if (df != NULL)
 			{
-				damage = FixedMul(damage, *pdf);
-				if (damage <= 0)
-					return;
+				fixed_t *pdf = df->CheckKey(mod);
+				if (pdf== NULL && mod != NAME_None) pdf = df->CheckKey(NAME_None);
+				if (pdf != NULL)
+				{
+					damage = FixedMul(damage, *pdf);
+					if (damage <= 0)
+						return;
+				}
 			}
+			damage = FixedMul(damage, target->DamageFactor);
+			if (damage < 0)
+				return;
 		}
-		damage = FixedMul(damage, target->DamageFactor);
-		if (damage < 0)
-			return;
 
 		damage = target->TakeSpecialDamage (inflictor, source, damage, mod);
 	}
diff --git a/src/p_local.h b/src/p_local.h
index 415ac46ca3..27654aafa2 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -468,6 +468,7 @@ enum EDmgFlags
 	DMG_INFLICTOR_IS_PUFF = 2,
 	DMG_THRUSTLESS = 4,
 	DMG_FORCED = 8,
+	DMG_NO_FACTOR = 16,
 };
 
 
diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index 441304ea18..cf8a2f5e40 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -1958,7 +1958,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_KillMaster)
 
 	if (self->master != NULL)
 	{
-		P_DamageMobj(self->master, self, self, self->master->health, damagetype, DMG_NO_ARMOR);
+		P_DamageMobj(self->master, self, self, self->master->health, damagetype, DMG_NO_ARMOR | DMG_NO_FACTOR);
 	}
 }
 
@@ -1979,7 +1979,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_KillChildren)
 	{
 		if (mo->master == self)
 		{
-			P_DamageMobj(mo, self, self, mo->health, damagetype, DMG_NO_ARMOR);
+			P_DamageMobj(mo, self, self, mo->health, damagetype, DMG_NO_ARMOR | DMG_NO_FACTOR);
 		}
 	}
 }
@@ -2001,7 +2001,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_KillSiblings)
 	{
 		if (mo->master == self->master && mo != self)
 		{
-			P_DamageMobj(mo, self, self, mo->health, damagetype, DMG_NO_ARMOR);
+			P_DamageMobj(mo, self, self, mo->health, damagetype, DMG_NO_ARMOR | DMG_NO_FACTOR);
 		}
 	}
 }