diff --git a/qbsp/map.cc b/qbsp/map.cc
index b8d61b90..a63b7a2b 100644
--- a/qbsp/map.cc
+++ b/qbsp/map.cc
@@ -1493,10 +1493,12 @@ static contentflags_t Brush_GetContents(const mapentity_t &entity, const mapbrus
     }
 
     if (string_iequals(entity.epairs.get("classname"), "func_illusionary_visblocker")) {
-        // unset solid + detail, set mist
+        // - unset existing visible contents + detail
+        // - set mist, mirrorinside, mirrorinside set
         // note this overrides the logic in face_get_contents() that normally forces mist to be detail
         base_contents = contentflags_t::make(
-            (base_contents.flags & ~(EWT_VISCONTENTS_SOLID | EWT_CFLAG_DETAIL)) | EWT_VISCONTENTS_MIST);
+            (base_contents.flags & ~(EWT_ALL_VISIBLE_CONTENTS | EWT_CFLAG_DETAIL))
+            | (EWT_VISCONTENTS_MIST | EWT_CFLAG_MIRROR_INSIDE | EWT_CFLAG_MIRROR_INSIDE_SET));
     }
 
     // non-Q2: -transwater implies liquids are detail
diff --git a/testmaps/q1_func_illusionary_visblocker.map b/testmaps/q1_func_illusionary_visblocker.map
index a84a6bd4..372be8ee 100644
--- a/testmaps/q1_func_illusionary_visblocker.map
+++ b/testmaps/q1_func_illusionary_visblocker.map
@@ -92,14 +92,13 @@
 // entity 3
 {
 "classname" "func_illusionary_visblocker"
-"_mirrorinside" "1"
 // brush 0
 {
-( -64 80 16 ) ( -64 81 16 ) ( -64 80 17 ) {trigger 0 0 0 1 1
-( -64 -16 16 ) ( -64 -16 17 ) ( -63 -16 16 ) {trigger 0 0 0 1 1
-( -64 80 16 ) ( -63 80 16 ) ( -64 81 16 ) {trigger 0 0 0 1 1
-( 176 128 240 ) ( 176 129 240 ) ( 177 128 240 ) {trigger 0 0 0 1 1
-( 176 16 32 ) ( 177 16 32 ) ( 176 16 33 ) {trigger 0 0 0 1 1
-( 176 128 32 ) ( 176 128 33 ) ( 176 129 32 ) {trigger 0 0 0 1 1
+( -64 80 16 ) ( -64 81 16 ) ( -64 80 17 ) *zwater1 0 0 0 1 1
+( -64 -16 16 ) ( -64 -16 17 ) ( -63 -16 16 ) *zwater1 0 0 0 1 1
+( -64 80 16 ) ( -63 80 16 ) ( -64 81 16 ) *zwater1 0 0 0 1 1
+( 176 128 240 ) ( 176 129 240 ) ( 177 128 240 ) *zwater1 0 0 0 1 1
+( 176 16 32 ) ( 177 16 32 ) ( 176 16 33 ) *zwater1 0 0 0 1 1
+( 176 128 32 ) ( 176 128 33 ) ( 176 129 32 ) *zwater1 0 0 0 1 1
 }
 }
diff --git a/tests/test_vis.cc b/tests/test_vis.cc
index 923bb331..51a8c901 100644
--- a/tests/test_vis.cc
+++ b/tests/test_vis.cc
@@ -106,9 +106,9 @@ TEST(vis, q1FuncIllusionaryVisblocker)
 {
     auto [bsp, bspx, lit] = QbspVisLight_Q1("q1_func_illusionary_visblocker.map", {}, runvis_t::yes);
 
-    // should export a face
-    auto *face = BSP_FindFaceAtPoint(&bsp, &bsp.dmodels[0], {80, 16, 96}, {0, 1, 0});
-    ASSERT_TRUE(face);
+    // func_illusionary_visblocker is 2 sided by default
+    EXPECT_TRUE(BSP_FindFaceAtPoint(&bsp, &bsp.dmodels[0], {80, 16, 96}, {0, 1, 0}));
+    EXPECT_TRUE(BSP_FindFaceAtPoint(&bsp, &bsp.dmodels[0], {80, 16, 96}, {0, -1, 0}));
 
     const auto vis = DecompressAllVis(&bsp);
 
@@ -126,6 +126,7 @@ TEST(vis, q1FuncIllusionaryVisblocker)
 
     EXPECT_EQ(item_enviro_leaf->contents, CONTENTS_EMPTY);
     EXPECT_EQ(player_start_leaf->contents, CONTENTS_EMPTY);
+    // water brush inside func_illusionary_visblocker gets converted to empty
     EXPECT_EQ(in_visblocker_leaf->contents, CONTENTS_EMPTY);
 
     // check visdata