diff --git a/common/bspfile.cc b/common/bspfile.cc
index a2d72f0f..dadb7a62 100644
--- a/common/bspfile.cc
+++ b/common/bspfile.cc
@@ -1254,12 +1254,16 @@ struct gamedef_q2_t : public gamedef_t
         }
 
         if (brushside_side == SIDE_BACK) {
+            // explicit override?
+            if (brushcontents.mirror_inside) {
+                return *brushcontents.mirror_inside;
+            }
             if (portal_visible_contents.native & Q2_CONTENTS_WINDOW) {
                 // windows don't generate inside faces
                 return false;
             }
-            // other types get mirrored by default, unless we override it with mirror_inside
-            return brushcontents.mirror_inside.value_or(true);
+            // other types get mirrored by default
+            return true;
         }
         return true;
     }
diff --git a/testmaps/qbsp_q2_mirrorinside.map b/testmaps/qbsp_q2_mirrorinside.map
index 632abd23..bd11d59c 100644
--- a/testmaps/qbsp_q2_mirrorinside.map
+++ b/testmaps/qbsp_q2_mirrorinside.map
@@ -88,3 +88,17 @@
 ( 112 -160 128 ) ( 112 -160 129 ) ( 112 -159 128 ) e1u1/brwater [ 0 1 0 0 ] [ 0 0 -1 0 ] 0 1 1 64 0 100
 }
 }
+// entity 3
+{
+"classname" "func_detail_fence"
+"_mirrorinside" "1"
+// brush 0
+{
+( 32 -428 112 ) ( 32 -427 112 ) ( 32 -428 113 ) e1u1/alphamask [ 0 1.0000000000000002 0 28 ] [ 0 0 -1.0000000000000002 -32 ] 0 1 1 1 33554432 0
+( 32 -380 112 ) ( 32 -380 113 ) ( 33 -380 112 ) e1u1/skip [ 1.0000000000000002 0 0 -16 ] [ 0 0 -1.0000000000000002 0 ] 0 1 1 1 128 0
+( 32 -428 112 ) ( 33 -428 112 ) ( 32 -427 112 ) e1u1/skip [ 1.0000000000000002 0 0 -16 ] [ 0 -1.0000000000000002 0 -28 ] 0 1 1 1 128 0
+( 112 -316 192 ) ( 112 -315 192 ) ( 113 -316 192 ) e1u1/skip [ 1.0000000000000002 0 0 -16 ] [ 0 1.0000000000000002 0 12 ] 0 1 1 1 128 0
+( 112 -316 128 ) ( 113 -316 128 ) ( 112 -316 129 ) e1u1/skip [ 1.0000000000000002 0 0 -16 ] [ 0 0 -1.0000000000000002 0 ] 0 1 1 1 128 0
+( 40 -316 128 ) ( 40 -316 129 ) ( 40 -315 128 ) e1u1/skip [ 0 -1.0000000000000002 0 -12 ] [ 0 0 -1.0000000000000002 0 ] 0 1 1 1 128 0
+}
+}
diff --git a/tests/test_qbsp_q2.cc b/tests/test_qbsp_q2.cc
index 3c42d194..0a7080f5 100644
--- a/tests/test_qbsp_q2.cc
+++ b/tests/test_qbsp_q2.cc
@@ -549,4 +549,10 @@ TEST_CASE("q2_mirrorinside" * doctest::test_suite("testmaps_q2"))
         CHECK_VECTORS_UNOREDERED_EQUAL(TexNames(bsp, BSP_FindFacesAtPoint(&bsp, &bsp.dmodels[0], mist_mirrorinside0_pos)),
             std::vector<std::string>({"e1u1/brwater"}));
     }
+
+    {
+        INFO("_mirrorinside 1 works on func_detail_fence");
+        CHECK_VECTORS_UNOREDERED_EQUAL(TexNames(bsp, BSP_FindFacesAtPoint(&bsp, &bsp.dmodels[0], {32, -348, 156})),
+            std::vector<std::string>({"e1u1/alphamask", "e1u1/alphamask"}));
+    }
 }