diff --git a/polymer/eduke32/build/include/build.h b/polymer/eduke32/build/include/build.h
index c6923dc66..418c1e67e 100644
--- a/polymer/eduke32/build/include/build.h
+++ b/polymer/eduke32/build/include/build.h
@@ -576,6 +576,9 @@ void   drawline256(int32_t x1, int32_t y1, int32_t x2, int32_t y2, char col);
 int32_t    printext16(int32_t xpos, int32_t ypos, int16_t col, int16_t backcol, const char *name, char fontsize) ATTRIBUTE((nonnull(5)));
 void   printext256(int32_t xpos, int32_t ypos, int16_t col, int16_t backcol, const char *name, char fontsize) ATTRIBUTE((nonnull(5)));
 
+void bfirst_search_init(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int32_t maxnum, int16_t firstelt);
+void bfirst_search_try(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int16_t elt);
+
 extern int32_t clipmoveboxtracenum;
 int32_t   clipmove(vec3_t *vect, int16_t *sectnum, int32_t xvect, int32_t yvect, int32_t walldist, int32_t ceildist, int32_t flordist, uint32_t cliptype) ATTRIBUTE((nonnull(1,2)));
 int32_t   clipinsidebox(int32_t x, int32_t y, int16_t wallnum, int32_t walldist);
@@ -586,6 +589,7 @@ int32_t   hitscan(const vec3_t *sv, int16_t sectnum, int32_t vx, int32_t vy, int
 int32_t   neartag(int32_t xs, int32_t ys, int32_t zs, int16_t sectnum, int16_t ange, int16_t *neartagsector, int16_t *neartagwall, int16_t *neartagsprite, int32_t *neartaghitdist, int32_t neartagrange, uint8_t tagsearch) ATTRIBUTE((nonnull(6,7,8)));
 int32_t   cansee(int32_t x1, int32_t y1, int32_t z1, int16_t sect1, int32_t x2, int32_t y2, int32_t z2, int16_t sect2);
 void   updatesector(int32_t x, int32_t y, int16_t *sectnum) ATTRIBUTE((nonnull(3)));
+void updatesector_onlynextwalls(int32_t x, int32_t y, int16_t *sectnum) ATTRIBUTE((nonnull(3)));
 void updatesectorexclude(int32_t x, int32_t y, int16_t *sectnum, const uint8_t *excludesectbitmap) ATTRIBUTE((nonnull(3)));
 void   updatesectorz(int32_t x, int32_t y, int32_t z, int16_t *sectnum) ATTRIBUTE((nonnull(4)));
 int32_t   inside(int32_t x, int32_t y, int16_t sectnum);
diff --git a/polymer/eduke32/build/include/editor.h b/polymer/eduke32/build/include/editor.h
index 726374da1..316609fbb 100644
--- a/polymer/eduke32/build/include/editor.h
+++ b/polymer/eduke32/build/include/editor.h
@@ -139,9 +139,6 @@ extern int32_t getinvdisplacement(int32_t *dx, int32_t *dy, int32_t dz) ATTRIBUT
 extern int32_t getscreenvdisp(int32_t bz, int32_t zoome);
 extern void setup_sideview_sincos(void);
 
-extern void bfirst_search_init(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int32_t maxnum, int16_t firstelt);
-extern void bfirst_search_try(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int16_t elt);
-
 extern int32_t wallength(int16_t i);
 extern void fixrepeats(int16_t i);
 extern uint32_t getlenbyrep(int32_t len, int32_t repeat);
diff --git a/polymer/eduke32/build/src/build.c b/polymer/eduke32/build/src/build.c
index afc0fbda3..2da8d9d94 100644
--- a/polymer/eduke32/build/src/build.c
+++ b/polymer/eduke32/build/src/build.c
@@ -2421,29 +2421,6 @@ static int32_t compare_wall_coords(const void *w1, const void *w2)
     } while (0)
 
 
-// breadth-first search helpers
-void bfirst_search_init(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int32_t maxnum, int16_t firstelt)
-{
-    Bmemset(bitmap, 0, (maxnum+7)>>3);
-
-    list[0] = firstelt;
-    bitmap[firstelt>>3] |= (1<<(firstelt&7));
-    *eltnumptr = 1;
-}
-
-void bfirst_search_try(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int16_t elt)
-{
-    if (elt < 0)
-        return;
-
-    if ((bitmap[elt>>3]&(1<<(elt&7)))==0)
-    {
-        bitmap[elt>>3] |= (1<<(elt&7));
-        list[*eltnumptr] = elt;
-        (*eltnumptr)++;
-    }
-}
-
 #ifdef YAX_ENABLE
 static int32_t collnumsects[2];
 static int16_t collsectlist[2][MAXSECTORS];
diff --git a/polymer/eduke32/build/src/engine.c b/polymer/eduke32/build/src/engine.c
index 068e1baeb..5d811fc99 100644
--- a/polymer/eduke32/build/src/engine.c
+++ b/polymer/eduke32/build/src/engine.c
@@ -12362,6 +12362,30 @@ int32_t pushmove(vec3_t *vect, int16_t *sectnum,
 }
 
 
+// breadth-first search helpers
+void bfirst_search_init(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int32_t maxnum, int16_t firstelt)
+{
+    Bmemset(bitmap, 0, (maxnum+7)>>3);
+
+    list[0] = firstelt;
+    bitmap[firstelt>>3] |= (1<<(firstelt&7));
+    *eltnumptr = 1;
+}
+
+void bfirst_search_try(int16_t *list, uint8_t *bitmap, int32_t *eltnumptr, int16_t elt)
+{
+    if (elt < 0)
+        return;
+
+    if ((bitmap[elt>>3]&(1<<(elt&7)))==0)
+    {
+        bitmap[elt>>3] |= (1<<(elt&7));
+        list[*eltnumptr] = elt;
+        (*eltnumptr)++;
+    }
+}
+
+
 //
 // updatesector[z]
 //
@@ -12401,6 +12425,39 @@ void updatesector(int32_t x, int32_t y, int16_t *sectnum)
     *sectnum = -1;
 }
 
+void updatesector_onlynextwalls(int32_t x, int32_t y, int16_t *sectnum)
+{
+    static int16_t sectlist[MAXSECTORS];
+    static uint8_t sectbitmap[MAXSECTORS>>3];
+    int32_t nsecs, sectcnt, j;
+
+    if ((unsigned)(*sectnum) >= (unsigned)numsectors)
+        return;
+
+    bfirst_search_init(sectlist, sectbitmap, &nsecs, numsectors, *sectnum);
+
+    for (sectcnt=0; sectcnt<nsecs; sectcnt++)
+    {
+        const sectortype *sec = &sector[sectlist[sectcnt]];
+        int32_t startwall = sec->wallptr;
+        int32_t endwall = sec->wallptr + sec->wallnum;
+
+        if (inside(x,y, sectlist[sectcnt]) == 1)
+        {
+            *sectnum = sectlist[sectcnt];
+            return;
+        }
+
+        for (j=startwall; j<endwall; j++)
+        {
+            if (wall[j].nextsector >= 0)
+                bfirst_search_try(sectlist, sectbitmap, &nsecs, wall[j].nextsector);
+        }
+    }
+
+    *sectnum = -1;
+}
+
 void updatesectorexclude(int32_t x, int32_t y, int16_t *sectnum, const uint8_t *excludesectbitmap)
 {
     walltype *wal;
diff --git a/polymer/eduke32/build/src/polymer.c b/polymer/eduke32/build/src/polymer.c
index 9c843f260..fb4e73719 100644
--- a/polymer/eduke32/build/src/polymer.c
+++ b/polymer/eduke32/build/src/polymer.c
@@ -993,10 +993,11 @@ void                polymer_drawrooms(int32_t daposx, int32_t daposy, int32_t da
     bglGetFloatv(GL_MODELVIEW_MATRIX, rootmodelviewmatrix);
 
     cursectnum = dacursectnum;
-    updatesector(daposx, daposy, &cursectnum);
-
+    updatesector_onlynextwalls(daposx, daposy, &cursectnum);
     if ((cursectnum >= 0) && (cursectnum < numsectors))
         dacursectnum = cursectnum;
+    else if (pr_verbosity>=2)
+        OSD_Printf("PR : got sector %d after update!\n", cursectnum);
 
     // unflag all sectors
     i = numsectors-1;
@@ -1034,6 +1035,9 @@ void                polymer_drawrooms(int32_t daposx, int32_t daposy, int32_t da
             (daposz > cursectflorz) ||
             (daposz < cursectceilz))
     {
+        if (!editstatus && pr_verbosity>=1)
+            OSD_Printf("PR : EXT sec=%d  z=%d (%d, %d)\n", dacursectnum, daposz, cursectflorz, cursectceilz);
+
         curmodelviewmatrix = rootmodelviewmatrix;
         i = numsectors-1;
         while (i >= 0)