diff --git a/polymer/eduke32/source/lunatic/util/build.lua b/polymer/eduke32/source/lunatic/util/build.lua
index 1fe60b084..62a4b4919 100644
--- a/polymer/eduke32/source/lunatic/util/build.lua
+++ b/polymer/eduke32/source/lunatic/util/build.lua
@@ -607,14 +607,15 @@ function loadarts(filenames)
     return tile
 end
 
-function readdefs(fn)
+-- defs [, rdefs] = readdefs(fn [, alsoreverse])
+function readdefs(fn, alsoreverse)
     local fh, errmsg = io.open(fn)
 
     if (fh==nil) then
         return nil, errmsg
     end
 
-    local defs = {}
+    local defs, rdefs = {}, nil
 
     for line in fh:lines() do
         local defname, numstr = string.match(line, "#?%s*define%s+([%a_][%w_]+)%s+([0-9]+)")
@@ -623,6 +624,13 @@ function readdefs(fn)
         end
     end
 
+    if (alsoreverse) then
+        rdefs = {}
+        for defname, num in pairs(defs) do
+            rdefs[num] = defname
+        end
+    end
+
     fh:close()
-    return defs
+    return defs, rdefs
 end
diff --git a/polymer/eduke32/source/lunatic/util/foreachmap.lua b/polymer/eduke32/source/lunatic/util/foreachmap.lua
index 35f35d7e9..a58251b9b 100755
--- a/polymer/eduke32/source/lunatic/util/foreachmap.lua
+++ b/polymer/eduke32/source/lunatic/util/foreachmap.lua
@@ -22,6 +22,8 @@
 --  $ ./findmaps.sh ~/.eduke32/ "sprite: .picnum>=d.CRACK1 and .picnum<=d.CRACK4"
 -- (Now: no space between "d." and "CRACK" is necessary ".xxx" is translated to
 -- "sprite[<current>].xxx" only if it's the name of a sprite member.)
+-- The local 'rdefs' provides the reverse mapping: from picnums to tile names
+-- (or nil).
 
 -- Print all V9 maps along with their number of bunches and max(ceilings of a bunch)
 --  $ prog='if (map.version==9) then print(map.numbunches.." ".. math.max(unpack(map.sectsperbunch[0],0)) .." "..fn) end'
@@ -119,7 +121,8 @@ if (modname:sub(1,2) == "-e") then
                 if (x==tab[i]) then return true end
             end
         end
-        local d=require('build').readdefs('../../names.h') or error('Need ../../names.h')  -- XXX
+        local d,rdefs = require('build').readdefs('../../names.h',true)
+        if (not d) then error('Need ../../names.h') end -- XXX
         local numsectors, numwalls, numsprites, sector, wall, sprite
         return function (map, fn)
             numsectors, numwalls, numsprites = map.numsectors, map.numwalls, map.numsprites