diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index 76e5592d..4b85f751 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -110,6 +110,7 @@
 #define CONTENTS_DETAIL -10     /* compiler internal use only */
 #define CONTENTS_DETAIL_ILLUSIONARY -11 /* compiler internal use only */
 #define CONTENTS_DETAIL_FENCE        -12   /* compiler internal use only */
+#define CONTENTS_ILLUSIONARY_VISBLOCKER -13
 
 // Special contents flags for the compiler only
 #define CFLAGS_STRUCTURAL_COVERED_BY_DETAIL (1U << 0)
diff --git a/qbsp/brush.cc b/qbsp/brush.cc
index 06fbf2d9..d22ea921 100644
--- a/qbsp/brush.cc
+++ b/qbsp/brush.cc
@@ -1122,11 +1122,18 @@ Brush_LoadEntity(mapentity_t *dst, const mapentity_t *src, const int hullnum)
     if (atoi(ValueForKey(src, "_mirrorinside"))) {
         cflags |= CFLAGS_BMODEL_MIRROR_INSIDE;
     }
-    
+
+    const bool func_illusionary_visblocker =
+        (0 == Q_strcasecmp(classname, "func_illusionary_visblocker"));
+
     for (i = 0; i < src->nummapbrushes; i++, mapbrush++) {
         mapbrush = &src->mapbrush(i);
         contents = Brush_GetContents(mapbrush);
 
+        /* FIXME: move into Brush_GetContents? */
+        if (func_illusionary_visblocker)
+            contents = CONTENTS_ILLUSIONARY_VISBLOCKER;
+
         /* "origin" brushes always discarded */
         if (contents == CONTENTS_ORIGIN)
             continue;
diff --git a/qbsp/map.cc b/qbsp/map.cc
index 3772316c..0070b6eb 100644
--- a/qbsp/map.cc
+++ b/qbsp/map.cc
@@ -1730,6 +1730,8 @@ IsWorldBrushEntity(const mapentity_t *entity)
         return true;
     if (!Q_strcasecmp(classname, "func_detail_fence"))
         return true;
+    if (!Q_strcasecmp(classname, "func_illusionary_visblocker"))
+        return true;
     return false;
 }
 
diff --git a/qbsp/portals.cc b/qbsp/portals.cc
index ec85c9e7..50a2c0ce 100644
--- a/qbsp/portals.cc
+++ b/qbsp/portals.cc
@@ -97,6 +97,10 @@ PortalThru(const portal_t *p)
     if (contents0 == CONTENTS_SOLID || contents1 == CONTENTS_SOLID)
         return false;
 
+    /* Can't see through func_illisionary_visblocker */
+    if (contents0 == CONTENTS_ILLUSIONARY_VISBLOCKER || contents1 == CONTENTS_ILLUSIONARY_VISBLOCKER)
+        return false;
+
     /* If contents values are the same and not solid, can see through */
     if (contents0 == contents1)
         return true;
diff --git a/qbsp/solidbsp.cc b/qbsp/solidbsp.cc
index 82b8038d..2f3f3ddc 100644
--- a/qbsp/solidbsp.cc
+++ b/qbsp/solidbsp.cc
@@ -28,6 +28,7 @@ int splitnodes;
 static int leaffaces;
 static int nodefaces;
 static int c_solid, c_empty, c_water, c_detail, c_detail_illusionary, c_detail_fence;
+static int c_illusionary_visblocker;
 static bool usemidsplit;
 
 //============================================================================
@@ -746,6 +747,9 @@ GetContentsName( int Contents ) {
         case CONTENTS_DETAIL_FENCE:
             return "DetailFence";
 
+        case CONTENTS_ILLUSIONARY_VISBLOCKER:
+            return "IllusionaryVisblocker";
+
         default:
             return "Error";
     }
@@ -767,7 +771,8 @@ int Contents_Priority(int contents)
         case CONTENTS_WATER:  return 2;
         case CONTENTS_SLIME:  return 2;
         case CONTENTS_LAVA:   return 2;
-            
+        case CONTENTS_ILLUSIONARY_VISBLOCKER: return 2;
+
         case CONTENTS_EMPTY:  return 1;
         case 0:               return 0;
         
@@ -846,6 +851,9 @@ LinkConvexFaces(surface_t *planelist, node_t *leafnode)
     case CONTENTS_DETAIL_FENCE:
         c_detail_fence++;
         break;
+    case CONTENTS_ILLUSIONARY_VISBLOCKER:
+        c_illusionary_visblocker++;
+        break;
     default:
         Error("Bad contents in face (%s)", __func__);
     }
@@ -1035,6 +1043,7 @@ SolidBSP(const mapentity_t *entity, surface_t *surfhead, bool midsplit)
     c_detail = 0;
     c_detail_illusionary = 0;
     c_detail_fence = 0;
+    c_illusionary_visblocker = 0;
 
     PartitionSurfaces(surfhead, headnode);
 
@@ -1045,6 +1054,7 @@ SolidBSP(const mapentity_t *entity, surface_t *surfhead, bool midsplit)
     Message(msgStat, "%8d detail leafs", c_detail);
     Message(msgStat, "%8d detail illusionary leafs", c_detail_illusionary);
     Message(msgStat, "%8d detail fence leafs", c_detail_fence);
+    Message(msgStat, "%8d illusionary visblocker leafs", c_illusionary_visblocker);
     Message(msgStat, "%8d leaffaces", leaffaces);
     Message(msgStat, "%8d nodefaces", nodefaces);
 
diff --git a/qbsp/writebsp.cc b/qbsp/writebsp.cc
index 153b57f1..801b3fde 100644
--- a/qbsp/writebsp.cc
+++ b/qbsp/writebsp.cc
@@ -55,6 +55,9 @@ RemapContentsForExport(int content)
          */
         return CONTENTS_SOLID;
     }
+    if (content == CONTENTS_ILLUSIONARY_VISBLOCKER) {
+        return CONTENTS_EMPTY;
+    }
     return content;
 }