diff --git a/filter.lua b/filter.lua
index ea255a0..7fbf2ec 100644
--- a/filter.lua
+++ b/filter.lua
@@ -135,7 +135,9 @@ local function collect_node(doc, l)
     }
     for _, t in ipairs(targets) do
         if nodes[t] then
-            table.insert(blocks, nodes[t]:clone())
+            local cl = nodes[t]:clone()
+            cl.identifier = ""
+            table.insert(blocks, cl)
             -- show("insert [" .. nodes[t].identifier .. ']\n')
         else
             io.stderr:write("Cannot find AST node with label " .. t .. "\n")
diff --git a/output.html b/output.html
index 102d986..1636cf0 100644
--- a/output.html
+++ b/output.html
@@ -4,10 +4,10 @@
 <p>thm2 - inthm2 (need thm1)</p>
 </div>
 <div id="inc" data-include="thm2, thm1 , fakelabel">
-<div id="thm2" class="Theorem">
+<div class="Theorem">
 <p>test thm2</p>
 <div id="inthm2" data-include="thm1">
-<div id="thm1" class="Theorem">
+<div class="Theorem">
 <p>test thm1</p>
 <div id="inthm1" class="Definition">
 <p>something</p>
@@ -15,7 +15,7 @@
 </div>
 </div>
 </div>
-<div id="thm1" class="Theorem">
+<div class="Theorem">
 <p>test thm1</p>
 <div id="inthm1" class="Definition">
 <p>something</p>
@@ -31,7 +31,7 @@
 <div id="thm2" class="Theorem">
 <p>test thm2</p>
 <div id="inthm2" data-include="thm1">
-<div id="thm1" class="Theorem">
+<div class="Theorem">
 <p>test thm1</p>
 <div id="inthm1" class="Definition">
 <p>something</p>