diff --git a/source/build/src/build.cpp b/source/build/src/build.cpp
index d65e10b42..6fdfba56c 100644
--- a/source/build/src/build.cpp
+++ b/source/build/src/build.cpp
@@ -7606,9 +7606,12 @@ end_space_handling:
                     }
 
                     newnumwalls = -1;
+                    char touchedwall[(MAXWALLS+7)>>3];
 
                     for (i=0; i<numdrawnwalls; i++)
                     {
+                        Bmemset(touchedwall, 0, sizeof(touchedwall));
+
                         for (j=numwalls-1; j>=0; j--)  /* j may be modified in loop */
                         {
                             vec2_t pint;
@@ -7616,6 +7619,9 @@ end_space_handling:
 
                             YAX_SKIPWALL(j);
 
+                            if (wall[j].nextwall >= 0 && (touchedwall[wall[j].nextwall>>3] & pow2char[wall[j].nextwall&7]))
+                                continue;
+
                             if (!lineintersect2v((vec2_t *)&wall[j], (vec2_t *)&POINT2(j),
                                                  &point[i], &point[i+1], &pint))
                                 continue;
@@ -7623,6 +7629,8 @@ end_space_handling:
                             if (vec2eq(&pint, (vec2_t *)&wall[j]) || vec2eq(&pint, (vec2_t *)&POINT2(j)))
                                 continue;
 
+                            touchedwall[j>>3] |= (1<<(j&7));
+
                             inspts = M32_InsertPoint(j, pint.x, pint.y, -1, &j);  /* maybe modify j */
 
                             if (inspts==0)