src/Pure/Isar/proof_context.ML

     val prt_typ = pretty_typ ctxt;
     val prt_sort = pretty_sort ctxt;
 
     (*theory*)
     val pretty_thy = Pretty.block
-      [Pretty.str "Theory:", Pretty.brk 1, Context.pretty_thy (theory_of ctxt)];  (* FIXME lowercase *)
+      [Pretty.str "theory:", Pretty.brk 1, Context.pretty_thy (theory_of ctxt)];
 
     (*defaults*)
     fun prt_atom prt prtT (x, X) = Pretty.block
       [prt x, Pretty.str " ::", Pretty.brk 1, prtT X];