src/Pure/Thy/thm_deps.ML

               if member (op =) parents' name then (gra', parents union parents')
               else (Symtab.update (name,
                 {name = Sign.base_name name, ID = name,
                  dir = space_implode "/" (session @ prefx),
                  unfold = false, path = "", parents = parents'}) gra',
-               name ins parents)
+               insert (op =) name parents)
             end
-          else (gra, name ins parents)
+          else (gra, insert (op =) name parents)
         else
           make_deps_graph prf' (gra, parents)
       end);
 
 fun thm_deps thms =