diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 21ddc8fe1..4e0901290 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,9 @@
 October 15, 2009  (Changes by Graf Zahl)
+- added ACS CheckActprClass function
+- fixed: When a blasted actor collided with another one this other actor's
+  DONTBLAST flag was not checked.
+- added a global DamageFactor actor property. All damage this actor takes is multiplied
+  by this factor in addition to damage type specific damage factors.
 - added better earthquake functions for ACS and DECORATE.
 
 October 10, 2009  (Changes by Graf Zahl)
diff --git a/src/actor.h b/src/actor.h
index 0b9605def..2c3b80108 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -850,6 +850,7 @@ public:
 	SWORD PainChance;
 	int PainThreshold;
 	FNameNoInit DamageType;
+	fixed_t DamageFactor;
 
 	FState *SpawnState;
 	FState *SeeState;
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 2e8f0050d..f7a5ef070 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -2429,6 +2429,7 @@ enum
 	APROP_NameTag		= 21,
 	APROP_Score			= 22,
 	APROP_Notrigger		= 23,
+	APROP_DamageFactor	= 24,
 };	
 
 // These are needed for ACS's APROP_RenderStyle
@@ -2593,6 +2594,10 @@ void DLevelScript::DoSetActorProperty (AActor *actor, int property, int value)
 		actor->Tag = FBehavior::StaticLookupString(value);
 		break;
 
+	case APROP_DamageFactor:
+		actor->DamageFactor = value;
+		break;
+
 	default:
 		// do nothing.
 		break;
@@ -2625,6 +2630,7 @@ int DLevelScript::GetActorProperty (int tid, int property)
 	case APROP_Health:		return actor->health;
 	case APROP_Speed:		return actor->Speed;
 	case APROP_Damage:		return actor->Damage;	// Should this call GetMissileDamage() instead?
+	case APROP_DamageFactor:return actor->DamageFactor;
 	case APROP_Alpha:		return actor->alpha;
 	case APROP_RenderStyle:	for (int style = STYLE_None; style < STYLE_Count; ++style)
 							{ // Check for a legacy render style that matches.
@@ -2685,6 +2691,7 @@ int DLevelScript::CheckActorProperty (int tid, int property, int value)
 		case APROP_Health:
 		case APROP_Speed:
 		case APROP_Damage:
+		case APROP_DamageFactor:
 		case APROP_Alpha:
 		case APROP_RenderStyle:
 		case APROP_Gravity:
@@ -2900,6 +2907,7 @@ enum EACSFunctions
 	ACSF_SetUserVariable,
 	ACSF_GetUserVariable,
 	ACSF_Radius_Quake2,
+	ACSF_CheckActorClass,
 };
 
 int DLevelScript::SideFromID(int id, int side)
@@ -3139,6 +3147,13 @@ int DLevelScript::CallFunction(int argCount, int funcIndex, SDWORD *args)
 			P_StartQuake(activator, args[0], args[1], args[2], args[3], args[4], FBehavior::StaticLookupString(args[5]));
 			break;
 
+		case ACSF_CheckActorClass:
+		{
+			AActor *a = args[0] == 0 ? (AActor *)activator : SingleActorFromTID(args[0], NULL); 
+			return a->GetClass()->TypeName == FName(FBehavior::StaticLookupString(args[1]));
+		}
+
+
 		default:
 			break;
 	}
diff --git a/src/p_interaction.cpp b/src/p_interaction.cpp
index 0602226f8..22d8cdc81 100644
--- a/src/p_interaction.cpp
+++ b/src/p_interaction.cpp
@@ -1009,6 +1009,8 @@ void P_DamageMobj (AActor *target, AActor *inflictor, AActor *source, int damage
 				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_map.cpp b/src/p_map.cpp
index 65ff3be78..644f599c6 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -886,8 +886,9 @@ bool PIT_CheckThing (AActor *thing, FCheckPosition &tm)
 	// Check for blasted thing running into another
 	if ((tm.thing->flags2 & MF2_BLASTED) && (thing->flags & MF_SHOOTABLE))
 	{
-		if (!(thing->flags2 & MF2_BOSS) && (thing->flags3 & MF3_ISMONSTER))
+		if (!(thing->flags2 & MF2_BOSS) && (thing->flags3 & MF3_ISMONSTER) && !(thing->flags3 & MF3_DONTBLAST))
 		{
+			// ideally this should take the mass factor into account
 			thing->velx += tm.thing->velx;
 			thing->vely += tm.thing->vely;
 			if ((thing->velx + thing->vely) > 3*FRACUNIT)
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index e898fd687..2285b9f9a 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -309,6 +309,10 @@ void AActor::Serialize (FArchive &arc)
 	{
 		arc << PainThreshold;
 	}
+	if (SaveVersion >= 1914)
+	{
+		arc << DamageFactor;
+	}
 
 	for(int i=0; i<10; i++) arc << uservar[i];
 
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index faa9fba46..2908eab65 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -924,18 +924,25 @@ DEFINE_PROPERTY(damagetype, S, Actor)
 //==========================================================================
 //
 //==========================================================================
-DEFINE_PROPERTY(damagefactor, SF, Actor)
+DEFINE_PROPERTY(damagefactor, ZF, Actor)
 {
 	PROP_STRING_PARM(str, 0);
 	PROP_FIXED_PARM(id, 1);
 
-	if (info->DamageFactors == NULL) info->DamageFactors=new DmgFactors;
+	if (str == NULL)
+	{
+		defaults->DamageFactor = id;
+	}
+	else
+	{
+		if (info->DamageFactors == NULL) info->DamageFactors=new DmgFactors;
 
-	FName dmgType;
-	if (!stricmp(str, "Normal")) dmgType = NAME_None;
-	else dmgType=str;
+		FName dmgType;
+		if (!stricmp(str, "Normal")) dmgType = NAME_None;
+		else dmgType=str;
 
-	(*info->DamageFactors)[dmgType]=id;
+		(*info->DamageFactors)[dmgType]=id;
+	}
 }
 
 //==========================================================================