diff --git a/themes/shortbread_v1/topics/boundaries.lua b/themes/shortbread_v1/topics/boundaries.lua
index 9d8aefd..fbba2cb 100644
--- a/themes/shortbread_v1/topics/boundaries.lua
+++ b/themes/shortbread_v1/topics/boundaries.lua
@@ -12,7 +12,7 @@ themepark:add_table{
     ids_type = 'way',
     geom = 'linestring',
     columns = themepark:columns({
-        { column = 'admin_level', type = 'int' },
+        { column = 'admin_level', type = 'int', not_null = true },
         { column = 'maritime', type = 'bool' },
         { column = 'disputed', type = 'bool' },
     }),
@@ -29,27 +29,24 @@ themepark:add_table{
     }
 }
 
-local rinfos = {}
-
 -- ---------------------------------------------------------------------------
+-- Storage of information from boundary relations for use by boundary ways
+-- (two-stage processing).
 
--- Check if this looks like a boundary and return admin_level as number
--- Return nil if this is not a valid boundary.
-local function get_admin_level(tags)
-    local type = tags.type
+-- Minimum admin level of all relations that reference a way id
+local min_admin_level = {}
 
-    if type == 'boundary' or type == 'multipolygon' then
-        local boundary = tags.boundary
-        if boundary == 'administrative' or boundary == 'disputed' then
-            return tonumber(tags.admin_level)
-        end
-    end
-end
+-- Minimum admin level of all relations tagged boundary=disputed that
+-- reference a way id
+local min_disputed_admin_level = {}
 
--- Check the (numeric) admin level. Change this depending on which admin
--- levels you want to process. Shortbread only shows 2 and 4.
-local function valid_admin_level(level)
-    return level == 2 or level == 4
+-- ---------------------------------------------------------------------------
+
+-- Shortbread is only interested in level 2 and level 4 admin boundaries.
+local function is_admin_boundary(tags)
+    return (tags.type == 'boundary' or tags.type == 'multipolygon')
+           and tags.boundary == 'administrative'
+           and (tags.admin_level == '2' or tags.admin_level == '4')
 end
 
 -- ---------------------------------------------------------------------------
@@ -59,16 +56,25 @@ themepark:add_proc('way', function(object, data)
         return
     end
 
-    local info = rinfos[object.id]
-    if not info then
+    local admin_level = min_admin_level[object.id]
+    if not admin_level then
         return
     end
 
     local t = object.tags
+
+    -- Set disputed flag either from disputed tag on the way...
+    local disputed = (t.disputed == 'yes')
+
+    -- .. or from a parent relation with boundary=disputed
+    if min_disputed_admin_level[object.id] and min_disputed_admin_level[object.id] <= admin_level then
+        disputed = true
+    end
+
     local a = {
-        admin_level = info.admin_level,
+        admin_level = admin_level,
         maritime = (t.maritime and (t.maritime == 'yes' or t.natural == 'coastline')),
-        disputed = info.disputed or (t.disputed and t.disputed == 'yes'),
+        disputed = disputed,
         geom = object:as_linestring()
     }
 
@@ -76,28 +82,35 @@ themepark:add_proc('way', function(object, data)
 end)
 
 themepark:add_proc('select_relation_members', function(relation)
-    if valid_admin_level(get_admin_level(relation.tags)) then
+    if is_admin_boundary(relation.tags) then
         return { ways = osm2pgsql.way_member_ids(relation) }
     end
 end)
 
 themepark:add_proc('relation', function(object, data)
-    local t = object.tags
+    if is_admin_boundary(object.tags) then
+        local admin_level = tonumber(object.tags.admin_level)
 
-    local admin_level = get_admin_level(t)
+        for _, id in ipairs(osm2pgsql.way_member_ids(object)) do
+            if not min_admin_level[id] or min_admin_level[id] > admin_level then
+                min_admin_level[id] = admin_level
+            end
+        end
 
-    if not valid_admin_level(admin_level) then
         return
     end
 
-    for _, member in ipairs(object.members) do
-        if member.type == 'w' then
-            if not rinfos[member.ref] then
-                rinfos[member.ref] = { admin_level = admin_level }
-            elseif rinfos[member.ref].admin_level > admin_level then
-                rinfos[member.ref].admin_level = admin_level
+    if object.tags.boundary == 'disputed' then
+        -- Ways in relations tagged boundary=disputed are flagged as disputed
+        -- if either the relation doesn't have an admin_level tag or the
+        -- admin_level tag is <= the admin level the way got from the
+        -- boundary=administrative relation(s).
+        local admin_level = tonumber(object.tags.admin_level) or 1
+
+        for _, id in ipairs(osm2pgsql.way_member_ids(object)) do
+            if not min_disputed_admin_level[id] or min_disputed_admin_level[id] > admin_level then
+                min_disputed_admin_level[id] = admin_level
             end
-            rinfos[member.ref].disputed = (t.boundary == 'disputed')
         end
     end
 end)