diff --git a/polymer/build/src/engine.c b/polymer/build/src/engine.c
index 7473ce8a5..bb2cb5df1 100644
--- a/polymer/build/src/engine.c
+++ b/polymer/build/src/engine.c
@@ -2462,8 +2462,10 @@ static void parascan(int dax1, int dax2, int sectnum, char dastat, int bunch)
     {
         wallnum = thewall[z]; nextsectnum = wall[wallnum].nextsector;
 
-        if (dastat == 0) j = sector[nextsectnum].ceilingstat;
-        else j = sector[nextsectnum].floorstat;
+        if(nextsectnum >= 0) { //else negative array access
+                if (dastat == 0) j = sector[nextsectnum].ceilingstat;
+                else j = sector[nextsectnum].floorstat;
+        }
 
         if ((nextsectnum < 0) || (wall[wallnum].cstat&32) || ((j&1) == 0))
         {