diff --git a/engine/client/cl_parse.c b/engine/client/cl_parse.c
index 9f105027a..21f1660bd 100644
--- a/engine/client/cl_parse.c
+++ b/engine/client/cl_parse.c
@@ -4774,7 +4774,7 @@ static void CL_ParseStaticProt (int baselinetype)
 	}
 
 	cl_static_entities[i].mdlidx = es.modelindex;
-	cl_static_entities[i].emit = NULL;
+	cl_static_entities[i].emit = trailkey_null;
 
 	cl_static_entities[i].state = es;
 	ent = &cl_static_entities[i].ent;
diff --git a/engine/client/cl_tent.c b/engine/client/cl_tent.c
index 5313d4bff..568487078 100644
--- a/engine/client/cl_tent.c
+++ b/engine/client/cl_tent.c
@@ -1065,8 +1065,8 @@ void CL_ParseStream (int type)
 				P_DelinkTrailstate(&b2->trailstate);
 				P_DelinkTrailstate(&b2->emitstate);
 				memcpy(b2, b, sizeof(*b2));
-				b2->trailstate = NULL;
-				b2->emitstate = NULL;
+				b2->trailstate = trailkey_null;
+				b2->emitstate = trailkey_null;
 				b2->alpha = 0.5;
 				b2->rflags = RF_TRANSLUCENT|RF_NOSHADOW;
 			}
diff --git a/engine/client/p_script.c b/engine/client/p_script.c
index 5707e2753..52ab65889 100644
--- a/engine/client/p_script.c
+++ b/engine/client/p_script.c
@@ -4159,7 +4159,7 @@ static void PScript_DelinkTrailstate(trailkey_t *tk)
 	}
 }
 
-static trailstate_t *P_NewTrailstate()
+static trailstate_t *P_NewTrailstate(void)
 {
 	trailstate_t *ts;
 
@@ -4954,7 +4954,7 @@ static int PScript_RunParticleEffectState (vec3_t org, vec3_t dir, float count,
 			p->rgba[3] += ptype->alpharand*frandom();
 			// p->color = 0;
 			if (ptype->emittime < 0)
-				p->state.trailstate = NULL;
+				p->state.trailstate = trailkey_null;
 			else
 				p->state.nextemit = particletime + ptype->emitstart - p->die;
 
@@ -5787,7 +5787,7 @@ static void P_ParticleTrailSpawn (vec3_t startpos, vec3_t end, part_type_t *ptyp
 
 		VectorClear (p->vel);
 		if (ptype->emittime < 0)
-			p->state.trailstate = NULL; // init trailstate
+			p->state.trailstate = trailkey_null; // init trailstate
 		else
 			p->state.nextemit = particletime + ptype->emitstart - p->die;
 
diff --git a/engine/client/pr_csqc.c b/engine/client/pr_csqc.c
index 9a0f91218..0d6712d9b 100644
--- a/engine/client/pr_csqc.c
+++ b/engine/client/pr_csqc.c
@@ -1048,7 +1048,7 @@ static void QCBUILTIN PF_cs_makestatic (pubprogfuncs_t *prinst, struct globalvar
 	{
 		entity_state_t *state = &cl_static_entities[cl.num_statics].state;
 		memset(state, 0, sizeof(*state));
-		cl_static_entities[cl.num_statics].emit = NULL;
+		cl_static_entities[cl.num_statics].emit = trailkey_null;
 		cl_static_entities[cl.num_statics].mdlidx = in->v->modelindex;
 		if (cl.worldmodel && cl.worldmodel->funcs.FindTouchedLeafs)
 			cl.worldmodel->funcs.FindTouchedLeafs(cl.worldmodel, &cl_static_entities[cl.num_statics].ent.pvscache, in->v->absmin, in->v->absmax);
@@ -3672,7 +3672,7 @@ void CSQC_ResetTrails(void)
 	for (i = 0; i < *prinst->parms->num_edicts; i++)
 	{
 		ent = (csqcedict_t*)EDICT_NUM_PB(prinst, i);
-		ent->trailstate = NULL;
+		ent->trailstate = trailkey_null;
 	}
 }
 
diff --git a/engine/client/r_surf.c b/engine/client/r_surf.c
index eeb5218a2..b86c7502d 100644
--- a/engine/client/r_surf.c
+++ b/engine/client/r_surf.c
@@ -4703,7 +4703,7 @@ TRACE(("dbg: Surf_NewMap: tp\n"));
 		}
 		if (cl.worldmodel && cl.worldmodel->loadstate == MLS_LOADED)
 			cl.worldmodel->funcs.FindTouchedLeafs(cl.worldmodel, &cl_static_entities[i].ent.pvscache, mins, maxs);
-		cl_static_entities[i].emit = NULL;
+		cl_static_entities[i].emit = trailkey_null;
 	}
 
 	CL_InitDlights();
diff --git a/engine/common/particles.h b/engine/common/particles.h
index 6446c463a..0f532a04b 100644
--- a/engine/common/particles.h
+++ b/engine/common/particles.h
@@ -167,6 +167,7 @@ extern int pt_q2[];
 #endif
 
 typedef quint32_t trailkey_t;
+#define trailkey_null 0
 
 #define PARTICLE_Z_CLIP	8.0