diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index 84b00747..a3156ecf 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -302,7 +302,7 @@ struct face_t
 {
     size_t planenum;
     int texinfo;
-    contentflags_t contents; // contents on the front of the face
+    twosided<contentflags_t> contents; // contents on the front/back of the face
     winding_t w;
     std::vector<size_t> original_vertices; // the vertices of this face before fragmentation; filled in by EmitVertices
     std::vector<face_fragment_t> fragments; // the vertices of this face post-fragmentation; filled in by TJunc
diff --git a/qbsp/exportobj.cc b/qbsp/exportobj.cc
index 0b78feae..b4605ca4 100644
--- a/qbsp/exportobj.cc
+++ b/qbsp/exportobj.cc
@@ -121,7 +121,7 @@ void ExportObj_Faces(const std::string &filesuffix, const std::vector<const face
 
     int vertcount = 0;
     for (const face_t *face : faces) {
-        std::string mtlname = fmt::format("contents{}\n", face->contents.native);
+        std::string mtlname = fmt::format("contents{}\n", face->contents.back.native);
 
         ExportObjFace(objfile, mtlname, face->w, face->get_texinfo(), &vertcount);
     }
diff --git a/qbsp/faces.cc b/qbsp/faces.cc
index 4731187d..cf950039 100644
--- a/qbsp/faces.cc
+++ b/qbsp/faces.cc
@@ -52,12 +52,12 @@ static bool ShouldOmitFace(face_t *f)
         return true;
 
     // HACK: to save a few faces, don't output the interior faces of sky brushes
-    if (f->contents.is_sky(qbsp_options.target_game)) {
+    if (f->contents.front.is_sky(qbsp_options.target_game)) {
         return true;
     }
 
     // omit faces fully covered by detail wall
-    if (f->contents.is_detail_wall(qbsp_options.target_game)) {
+    if (f->contents.front.is_detail_wall(qbsp_options.target_game)) {
         return true;
     }
 
@@ -138,7 +138,7 @@ Returns a global edge number, possibly negative to indicate a backwards edge.
 */
 inline int64_t GetEdge(const size_t &v1, const size_t &v2, const face_t *face, emit_faces_stats_t &stats)
 {
-    if (!face->contents.is_valid(qbsp_options.target_game, false))
+    if (!face->contents.front.is_valid(qbsp_options.target_game, false))
         FError("Face with invalid contents");
 
     // search for existing edges
@@ -495,7 +495,7 @@ static std::unique_ptr<face_t> FaceFromPortal(portal_t *p, bool pside)
         f->w = p->winding.clone();
     }
 
-    f->contents = p->nodes[pside]->contents;
+    f->contents = {.front = p->nodes[pside]->contents, .back = p->nodes[!pside]->contents};
 
     UpdateFaceSphere(f.get());