diff --git a/src/pylorax/treebuilder.py b/src/pylorax/treebuilder.py
index 9159c1cc..2d8e7cea 100644
--- a/src/pylorax/treebuilder.py
+++ b/src/pylorax/treebuilder.py
@@ -148,7 +148,7 @@ class TreeBuilder(BaseBuilder):
                 initrd.write(cpio.read())
 
     def implantisomd5(self):
-        for section, data in self.treeinfo_data:
+        for section, data in self.treeinfo_data.items():
             if 'boot.iso' in data:
                 iso = joinpaths(self.outputdir, data['boot.iso'])
                 check_call(["implantisomd5", iso])