diff --git a/polymer/eduke32/source/lunatic/defs.ilua b/polymer/eduke32/source/lunatic/defs.ilua
index a58fec931..d34e706bb 100644
--- a/polymer/eduke32/source/lunatic/defs.ilua
+++ b/polymer/eduke32/source/lunatic/defs.ilua
@@ -951,8 +951,8 @@ end
 
 local tile_static_members = defs_c.static_members_tab()
 do
-    tile_static_members.sizx = defs_c.creategtab(ffiC.tilesizx, ffiC.MAXTILES, "tilesizx[]")
-    tile_static_members.sizy = defs_c.creategtab(ffiC.tilesizy, ffiC.MAXTILES, "tilesizy[]")
+    tile_static_members.sizx = defs_c.creategtab_membidx(ffiC.tilesiz, "x", ffiC.MAXTILES, "tilesizx[]")
+    tile_static_members.sizy = defs_c.creategtab_membidx(ffiC.tilesiz, "y", ffiC.MAXTILES, "tilesizy[]")
 end
 
 -- XXX: error message will say "g_player_ps"
diff --git a/polymer/eduke32/source/lunatic/defs_common.lua b/polymer/eduke32/source/lunatic/defs_common.lua
index e36be26cc..cf7405597 100644
--- a/polymer/eduke32/source/lunatic/defs_common.lua
+++ b/polymer/eduke32/source/lunatic/defs_common.lua
@@ -444,7 +444,7 @@ int32_t guniqhudid;
 const int16_t headspritesect[MAXSECTORS+1], headspritestat[MAXSTATUS+1];
 const int16_t prevspritesect[MAXSPRITES], prevspritestat[MAXSPRITES];
 const int16_t nextspritesect[MAXSPRITES], nextspritestat[MAXSPRITES];
-const int16_t tilesizx[MAXTILES], tilesizy[MAXTILES];
+const vec2_t tilesiz[MAXTILES];
 
 uint8_t show2dsector[(MAXSECTORS+7)>>3];
 
@@ -849,7 +849,7 @@ end
 
 ---- indirect C array access ----
 
--- create a safe indirection for an ffi.C array
+-- Create a safe indirection for an ffi.C array.
 function creategtab(ctab, maxidx, name)
     local tab = {}
     local tmpmt = {
@@ -867,6 +867,25 @@ function creategtab(ctab, maxidx, name)
     return setmtonce(tab, tmpmt)
 end
 
+-- Create a a safe indirection for an ffi.C struct array, accessing a given
+-- member.
+function creategtab_membidx(ctab, membname, maxidx, name)
+    local tab = {}
+    local tmpmt = {
+        __index = function(tab, key)
+            if (key>=0 and key < maxidx) then
+                return ctab[key][membname]
+            end
+            error('out-of-bounds '..name..' read access', 2)
+        end,
+        __newindex = function()
+            error('cannot write directly to '..name, 2)
+        end,
+    }
+
+    return setmtonce(tab, tmpmt)
+end
+
 -- Construct const struct from table
 function conststruct(tab)
     local strtab = { "struct {" }
diff --git a/polymer/eduke32/source/lunatic/dynsymlist b/polymer/eduke32/source/lunatic/dynsymlist
index de3de841c..8b87ff7fa 100644
--- a/polymer/eduke32/source/lunatic/dynsymlist
+++ b/polymer/eduke32/source/lunatic/dynsymlist
@@ -46,8 +46,7 @@ prevspritesect;
 prevspritestat;
 nextspritesect;
 nextspritestat;
-tilesizx;
-tilesizy;
+tilesiz;
 
 show2dsector;
 
diff --git a/polymer/eduke32/source/lunatic/dynsymlist_m32 b/polymer/eduke32/source/lunatic/dynsymlist_m32
index 040ba9f57..27d17d4b6 100644
--- a/polymer/eduke32/source/lunatic/dynsymlist_m32
+++ b/polymer/eduke32/source/lunatic/dynsymlist_m32
@@ -46,8 +46,7 @@ prevspritesect;
 prevspritestat;
 nextspritesect;
 nextspritestat;
-tilesizx;
-tilesizy;
+tilesiz;
 
 show2dsector;