diff --git a/src/actor.h b/src/actor.h
index eb95c0bbd7..32bc260548 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -297,6 +297,7 @@ enum
 	MF5_ALWAYSRESPAWN	= 0x00020000,	// always respawns, regardless of skill setting
 	MF5_NEVERRESPAWN	= 0x00040000,	// never respawns, regardless of skill setting
 	MF5_DONTRIP			= 0x00080000,	// Ripping projectiles explode when hittin this actor
+	MF5_NOINFIGHTING	= 0x00100000,	// This actor doesn't switch target when it's hurt 
 
 
 // --- mobj.renderflags ---
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index 32f236e3b3..06c03792f8 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -234,6 +234,7 @@ static flagdef ActorFlags[]=
 	DEFINE_FLAG(MF5, ALWAYSRESPAWN, AActor, flags5),
 	DEFINE_FLAG(MF5, NEVERRESPAWN, AActor, flags5),
 	DEFINE_FLAG(MF5, DONTRIP, AActor, flags5),
+	DEFINE_FLAG(MF5, NOINFIGHTING, AActor, flags5),
 
 	// Effect flags
 	DEFINE_FLAG(FX, VISIBILITYPULSE, AActor, effects),