diff --git a/src/p_saveg.c b/src/p_saveg.c
index 1c8d46aa1..e0d3f1e94 100644
--- a/src/p_saveg.c
+++ b/src/p_saveg.c
@@ -1687,6 +1687,7 @@ static void SaveFadeColormapThinker(const thinker_t *th, const UINT8 type)
 	WRITEUINT32(save_p, SaveSector(ht->sector));
 	SaveExtraColormap(save_p, ht->source_exc);
 	SaveExtraColormap(save_p, ht->dest_exc);
+	WRITEUINT8(save_p, (UINT8)ht->ticbased);
 	WRITEINT32(save_p, ht->duration);
 	WRITEINT32(save_p, ht->timer);
 }
@@ -2686,6 +2687,7 @@ static inline void LoadFadeColormapThinker(actionf_p1 thinker)
 	ht->sector = LoadSector(READUINT32(save_p));
 	ht->source_exc = LoadExtraColormap(save_p);
 	ht->dest_exc = LoadExtraColormap(save_p);
+	ht->ticbased = (boolean)READUINT8(save_p);
 	ht->duration = READINT32(save_p);
 	ht->timer = READINT32(save_p);
 	if (ht->sector)
diff --git a/src/p_spec.c b/src/p_spec.c
index 491671c40..bed5a89b4 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -105,7 +105,7 @@ static void Add_Pusher(pushertype_e type, fixed_t x_mag, fixed_t y_mag, mobj_t *
 static void Add_MasterDisappearer(tic_t appeartime, tic_t disappeartime, tic_t offset, INT32 line, INT32 sourceline);
 static void P_ResetColormapFader(sector_t *sector);
 static void Add_ColormapFader(sector_t *sector, extracolormap_t *source_exc, extracolormap_t *dest_exc,
-	INT32 duration);
+	boolean ticbased, INT32 duration);
 static void P_AddBlockThinker(sector_t *sec, line_t *sourceline);
 static void P_AddFloatThinker(sector_t *sec, INT32 tag, line_t *sourceline);
 //static void P_AddBridgeThinker(line_t *sourceline, sector_t *sec);
@@ -3445,7 +3445,7 @@ static void P_ProcessLineSpecial(line_t *line, mobj_t *mo, sector_t *callsec)
 				else
 					Z_Free(exc);
 
-				Add_ColormapFader(&sectors[secnum], source_exc, dest_exc,
+				Add_ColormapFader(&sectors[secnum], source_exc, dest_exc, (line->flags & ML_EFFECT4), // tic-based timing
 					(line->sidenum[1] != 0xFFFF ? abs(sides[line->sidenum[1]].rowoffset >> FRACBITS) : abs(P_AproxDistance(line->dx, line->dy) >> FRACBITS)));
 			}
 			break;
@@ -7480,7 +7480,7 @@ static void P_ResetColormapFader(sector_t *sector)
 }
 
 static void Add_ColormapFader(sector_t *sector, extracolormap_t *source_exc, extracolormap_t *dest_exc,
-	INT32 duration)
+	boolean ticbased, INT32 duration)
 {
 	P_ResetColormapFader(sector);
 
@@ -7496,7 +7496,18 @@ static void Add_ColormapFader(sector_t *sector, extracolormap_t *source_exc, ext
 	d->sector = sector;
 	d->source_exc = source_exc;
 	d->dest_exc = dest_exc;
-	d->duration = d->timer = duration;
+
+	if (ticbased)
+	{
+		d->ticbased = true;
+		d->duration = d->timer = duration;
+	}
+	else
+	{
+		d->ticbased = false;
+		d->timer = 256;
+		d->duration = duration; // use as speed
+	}
 
 	sector->fadecolormapdata = d;
 	P_AddThinker(&d->thinker); // add thinker
@@ -7504,7 +7515,8 @@ static void Add_ColormapFader(sector_t *sector, extracolormap_t *source_exc, ext
 
 void T_FadeColormap(fadecolormap_t *d)
 {
-	if (--d->timer <= 0)
+	if ((d->ticbased && --d->timer <= 0)
+		|| (!d->ticbased && (d->timer -= d->duration) <= 0)) // d->duration used as speed decrement
 	{
 		d->sector->extra_colormap = d->dest_exc;
 		P_ResetColormapFader(d->sector);
@@ -7512,7 +7524,8 @@ void T_FadeColormap(fadecolormap_t *d)
 	else
 	{
 		extracolormap_t *exc;
-		fixed_t factor = min(FixedDiv(d->duration - d->timer, d->duration), 1*FRACUNIT);
+		INT32 duration = d->ticbased ? d->duration : 256;
+		fixed_t factor = min(FixedDiv(duration - d->timer, duration), 1*FRACUNIT);
 		INT16 cr, cg, cb, ca, fadestart, fadeend, fog;
 		INT32 rgba, fadergba;
 
diff --git a/src/p_spec.h b/src/p_spec.h
index 9e0b7d5c4..0a798ffcc 100644
--- a/src/p_spec.h
+++ b/src/p_spec.h
@@ -461,8 +461,9 @@ typedef struct
 	sector_t *sector;           ///< Sector where action is taking place.
 	extracolormap_t *source_exc;
 	extracolormap_t *dest_exc;
-	INT32 duration;             ///< Total duration for tic-based logic
-	INT32 timer;                ///< Timer for tic-based logic
+	boolean ticbased;           ///< Tic-based timing
+	INT32 duration;             ///< Total duration for tic-based logic (OR: speed increment)
+	INT32 timer;                ///< Timer for tic-based logic (OR: internal speed counter)
 } fadecolormap_t;
 
 void T_FadeColormap(fadecolormap_t *d);