diff --git a/src/p_effect.cpp b/src/p_effect.cpp
index 7aff1c5cc..7919b8d46 100644
--- a/src/p_effect.cpp
+++ b/src/p_effect.cpp
@@ -321,7 +321,7 @@ enum PSFlag
 };
 
 void P_SpawnParticle(const DVector3 &pos, const DVector3 &vel, const DVector3 &accel, PalEntry color, double startalpha, int lifetime, double size, 
-	double fadestep, double endsize, int flags)
+	double fadestep, double sizestep, int flags)
 {
 	particle_t *particle = NewParticle();
 
@@ -337,7 +337,7 @@ void P_SpawnParticle(const DVector3 &pos, const DVector3 &vel, const DVector3 &a
 		particle->ttl = lifetime;
 		particle->bright = !!(flags & PS_FULLBRIGHT);
 		particle->size = size;
-		particle->sizestep = (lifetime == 0) ? 0 : ((endsize - size) / lifetime);
+		particle->sizestep = sizestep;
 		particle->notimefreeze = !!(flags & PS_NOTIMEFREEZE);
 	}
 }
diff --git a/src/p_effect.h b/src/p_effect.h
index 2414372c3..614702a49 100644
--- a/src/p_effect.h
+++ b/src/p_effect.h
@@ -85,7 +85,7 @@ particle_t *JitterParticle (int ttl);
 particle_t *JitterParticle (int ttl, double drift);
 
 void P_ThinkParticles (void);
-void P_SpawnParticle(const DVector3 &pos, const DVector3 &vel, const DVector3 &accel, PalEntry color, double startalpha, int lifetime, double size, double fadestep, double endsize, int flags = 0);
+void P_SpawnParticle(const DVector3 &pos, const DVector3 &vel, const DVector3 &accel, PalEntry color, double startalpha, int lifetime, double size, double fadestep, double sizestep, int flags = 0);
 void P_InitEffects (void);
 void P_RunEffects (void);
 
diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index dbbb12f6a..9c8464417 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -3199,7 +3199,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_SpawnParticle)
 	PARAM_FLOAT_OPT	(accelz)		{ accelz = 0; }
 	PARAM_FLOAT_OPT	(startalpha)	{ startalpha = 1.; }
 	PARAM_FLOAT_OPT	(fadestep)		{ fadestep = -1.; }
-	PARAM_FLOAT_OPT (endsize)		{ endsize = -1.; }
+	PARAM_FLOAT_OPT (sizestep)		{ sizestep = 0.; }
 
 	startalpha = clamp(startalpha, 0., 1.);
 	if (fadestep > 0) fadestep = clamp(fadestep, 0., 1.);
@@ -3230,7 +3230,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_SpawnParticle)
 			acc.X = accelx * c + accely * s;
 			acc.Y = accelx * s - accely * c;
 		}
-		P_SpawnParticle(self->Vec3Offset(pos), vel, acc, color, startalpha, lifetime, size, fadestep, endsize, flags);
+		P_SpawnParticle(self->Vec3Offset(pos), vel, acc, color, startalpha, lifetime, size, fadestep, sizestep, flags);
 	}
 	return 0;
 }
diff --git a/wadsrc/static/actors/actor.txt b/wadsrc/static/actors/actor.txt
index 5c46d0d4b..2ce48b036 100644
--- a/wadsrc/static/actors/actor.txt
+++ b/wadsrc/static/actors/actor.txt
@@ -215,7 +215,7 @@ ACTOR Actor native //: Thinker
 	native void A_SetScale(float scalex, float scaley = 0, int ptr = AAPTR_DEFAULT, bool usezero = false);
 	native void A_SetMass(int mass);
 	native void A_SpawnDebris(class<Actor> spawntype, bool transfer_translation = false, float mult_h = 1, float mult_v = 1);
-	native void A_SpawnParticle(color color1, int flags = 0, int lifetime = 35, float size = 1, float angle = 0, float xoff = 0, float yoff = 0, float zoff = 0, float velx = 0, float vely = 0, float velz = 0, float accelx = 0, float accely = 0, float accelz = 0, float startalphaf = 1, float fadestepf = -1, float endsize = -1);
+	native void A_SpawnParticle(color color1, int flags = 0, int lifetime = 35, float size = 1, float angle = 0, float xoff = 0, float yoff = 0, float zoff = 0, float velx = 0, float vely = 0, float velz = 0, float accelx = 0, float accely = 0, float accelz = 0, float startalphaf = 1, float fadestepf = -1, float sizestep = 0);
 	native state A_CheckSight(state label);
 	native void A_ExtChase(bool usemelee, bool usemissile, bool playactive = true, bool nightmarefast = false);
 	native void A_DropInventory(class<Inventory> itemtype);