diff --git a/src/protocol/ast.rs b/src/protocol/ast.rs
index 3510e80f484af804fb41047d1ff0c38d14abd87c..2e5bdc8d168c3eba253195ba4b8075f3313e7a88 100644
--- a/src/protocol/ast.rs
+++ b/src/protocol/ast.rs
@@ -642,8 +642,8 @@ impl ConcreteType {
                     for poly_arg_idx in 0..num_poly_args {
                         if poly_arg_idx != 0 {
                             target.push(',');
-                            idx = Self::render_type_part_at(parts, heap, idx, target);
                         }
+                        idx = Self::render_type_part_at(parts, heap, idx, target);
                     }
                     target.push('>');
                 }