diff --git a/src/frontends/lean/pp.cpp b/src/frontends/lean/pp.cpp
index e4207051eb..a34874ee08 100644
--- a/src/frontends/lean/pp.cpp
+++ b/src/frontends/lean/pp.cpp
@@ -1140,7 +1140,7 @@ auto pretty_fn::pp_mdata(expr const & e) -> result {
 
 auto pretty_fn::pp_proj(expr const & e) -> result {
     format arg_fmt = pp_child(proj_expr(e), max_bp()).fmt();
-    format idx_fmt(proj_idx(e).get_small_value());
+    format idx_fmt(proj_idx(e).get_small_value() + 1);
     return result(arg_fmt + format(".") + idx_fmt);
 }