diff --git a/extras/conf/udb/Includes/SRB222_linedefs.cfg b/extras/conf/udb/Includes/SRB222_linedefs.cfg
index 2ec7691ab..a75c98b4d 100644
--- a/extras/conf/udb/Includes/SRB222_linedefs.cfg
+++ b/extras/conf/udb/Includes/SRB222_linedefs.cfg
@@ -2660,7 +2660,7 @@ udmf
 			}
 			arg2
 			{
-				title = "Speed";
+				title = "Fading speed";
 			}
 			arg3
 			{
@@ -2668,8 +2668,9 @@ udmf
 				type = 12;
 				enum
 				{
-					1 = "Speed is tic duration";
-					2 = "Override existing fade";
+					1 = "Add to current translucency";
+					2 = "Interrupt ongoing fades";
+					4 = "Speed is duration";
 				}
 			}
 		}
diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index 350c1585f..7c1d61a9c 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -2342,9 +2342,10 @@ static int lib_pFadeLight(lua_State *L)
 	INT32 speed = (INT32)luaL_checkinteger(L, 3);
 	boolean ticbased = lua_optboolean(L, 4);
 	boolean force = lua_optboolean(L, 5);
+	boolean relative = lua_optboolean(L, 6);
 	NOHUD
 	INLEVEL
-	P_FadeLight(tag, destvalue, speed, ticbased, force);
+	P_FadeLight(tag, destvalue, speed, ticbased, force, relative);
 	return 0;
 }
 
diff --git a/src/p_lights.c b/src/p_lights.c
index e8da48e9a..58ab2e799 100644
--- a/src/p_lights.c
+++ b/src/p_lights.c
@@ -358,9 +358,10 @@ void P_FadeLightBySector(sector_t *sector, INT32 destvalue, INT32 speed, boolean
 	}
 }
 
-void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased, boolean force)
+void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased, boolean force, boolean relative)
 {
 	INT32 i;
+	INT32 realdestvalue;
 
 	// search all sectors for ones with tag
 	TAG_ITER_SECTORS(tag, i)
@@ -373,7 +374,9 @@ void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased, bool
 			CONS_Debug(DBG_GAMELOGIC, "Line type 420 Executor: Fade light thinker already exists, timer: %d\n", ((lightlevel_t*)sectors[i].lightingdata)->timer);
 			continue;
 		}
-		P_FadeLightBySector(&sectors[i], destvalue, speed, ticbased);
+
+		realdestvalue = relative ? max(0, min(255, sectors[i].lightlevel + destvalue)) : destvalue;
+		P_FadeLightBySector(&sectors[i], realdestvalue, speed, ticbased);
 	}
 }
 
diff --git a/src/p_setup.c b/src/p_setup.c
index b87df4090..251e0fbb3 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3745,7 +3745,7 @@ static void P_ConvertBinaryMap(void)
 			if (lines[i].flags & ML_EFFECT4)
 				lines[i].args[3] |= TMF_TICBASED;
 			if (lines[i].flags & ML_EFFECT5)
-				lines[i].args[3] |= TMF_FORCE;
+				lines[i].args[3] |= TMF_OVERRIDE;
 			break;
 		case 421: //Stop lighting effect
 			lines[i].args[0] = tag;
diff --git a/src/p_spec.c b/src/p_spec.c
index 2737c4d24..aeb657988 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -2527,7 +2527,7 @@ static void P_ProcessLineSpecial(line_t *line, mobj_t *mo, sector_t *callsec)
 			break;
 
 		case 420: // Fade light levels in tagged sectors to new value
-			P_FadeLight(line->args[0], line->args[1], line->args[2], line->args[3] & TMF_TICBASED, line->args[3] & TMF_FORCE);
+			P_FadeLight(line->args[0], line->args[1], line->args[2], line->args[3] & TMF_TICBASED, line->args[3] & TMF_OVERRIDE, line->args[3] & TMF_RELATIVE);
 			break;
 
 		case 421: // Stop lighting effect in tagged sectors
diff --git a/src/p_spec.h b/src/p_spec.h
index d759b701b..ca0bf0cb3 100644
--- a/src/p_spec.h
+++ b/src/p_spec.h
@@ -121,8 +121,9 @@ typedef enum
 
 typedef enum
 {
-	TMF_TICBASED = 1,
-	TMF_FORCE    = 1<<1,
+	TMF_RELATIVE = 1,
+	TMF_OVERRIDE = 1<<1,
+	TMF_TICBASED = 1<<2,
 } textmapfadeflags_t;
 
 typedef enum
@@ -301,7 +302,7 @@ void T_Glow(glow_t *g);
 glow_t *P_SpawnAdjustableGlowingLight(sector_t *sector, INT16 lighta, INT16 lightb, INT32 length);
 
 void P_FadeLightBySector(sector_t *sector, INT32 destvalue, INT32 speed, boolean ticbased);
-void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased, boolean force);
+void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased, boolean force, boolean relative);
 void T_LightFade(lightlevel_t *ll);
 
 typedef enum