diff --git a/doomsday/engine/portable/src/edit_bsp.c b/doomsday/engine/portable/src/edit_bsp.c
index 5f52ee6c45..700bec23c2 100644
--- a/doomsday/engine/portable/src/edit_bsp.c
+++ b/doomsday/engine/portable/src/edit_bsp.c
@@ -188,27 +188,6 @@ static void buildHEdgesFromBSPHEdges(GameMap* dest, BinaryTree* rootNode)
 
         if(hedge->length == 0)
             hedge->length = 0.01f; // Hmm...
-
-        // Calculate the tangent space surface vectors.
-        if(hedge->lineDef && HEDGE_SIDEDEF(hedge))
-        {
-            SideDef* side = HEDGE_SIDEDEF(hedge);
-            Surface* surface = &side->SW_topsurface;
-
-            surface->normal[VY] = (hedge->HE_v1pos[VX] - hedge->HE_v2pos[VX]) / hedge->length;
-            surface->normal[VX] = (hedge->HE_v2pos[VY] - hedge->HE_v1pos[VY]) / hedge->length;
-            surface->normal[VZ] = 0;
-            V3f_BuildTangents(surface->tangent, surface->bitangent, surface->normal);
-
-            // All surfaces of a sidedef have the same tangent space vectors.
-            memcpy(side->SW_middletangent, surface->tangent, sizeof(surface->tangent));
-            memcpy(side->SW_middlebitangent, surface->bitangent, sizeof(surface->bitangent));
-            memcpy(side->SW_middlenormal, surface->normal, sizeof(surface->normal));
-
-            memcpy(side->SW_bottomtangent, surface->tangent, sizeof(surface->tangent));
-            memcpy(side->SW_bottombitangent, surface->bitangent, sizeof(surface->bitangent));
-            memcpy(side->SW_bottomnormal, surface->normal, sizeof(surface->normal));
-        }
     }
 
     // Free temporary storage
diff --git a/doomsday/engine/portable/src/edit_map.c b/doomsday/engine/portable/src/edit_map.c
index 4f82e2de50..b4b91f5e9f 100644
--- a/doomsday/engine/portable/src/edit_map.c
+++ b/doomsday/engine/portable/src/edit_map.c
@@ -772,6 +772,17 @@ static void finishSectors(GameMap* map)
     }
 }
 
+static void finishSideDefs(GameMap* map)
+{
+    uint i;
+    // Calculate the tangent space surface vectors.
+    for(i = 0; i < map->numSideDefs; ++i)
+    {
+        SideDef* side = &map->sideDefs[i];
+        SideDef_UpdateSurfaceTangents(side);
+    }
+}
+
 static void finishLineDefs(GameMap* map)
 {
     uint i;
@@ -1764,6 +1775,7 @@ boolean MPE_End(void)
     }
 
     buildSectorLineLists(gamemap);
+    finishSideDefs(gamemap);
     finishLineDefs(gamemap);
     finishSectors(gamemap);
     updateMapBounds(gamemap);