diff --git a/Project.toml b/Project.toml
index 0315ac8..7f71e25 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "MixedStructTypes"
 uuid = "3d69f371-6fa5-5add-b11c-3293622cad62"
-version = "0.2.3"
+version = "0.2.4"
 
 [deps]
 ExprTools = "e2ba6199-217a-4e67-a87a-7c52f15ade04"
diff --git a/src/SumStructs.jl b/src/SumStructs.jl
index ef8d0c3..c4823cc 100644
--- a/src/SumStructs.jl
+++ b/src/SumStructs.jl
@@ -25,10 +25,20 @@ macro sum_structs(type, struct_defs)
     
     variants_types = []
     hidden_struct_types = []
+    variants_params_unconstr = [[] for _ in 1:length(struct_defs)]
+
+    fields_each, default_each = [], []
+    for a_spec in struct_defs
+        a_comps = decompose_struct_no_base(a_spec)
+        push!(fields_each, a_comps[2][1])
+        push!(default_each, a_comps[2][2])
+    end
+
     for (i, d) in enumerate(struct_defs)
         t = d.args[2]
         c = @capture(t, t_n_{t_p__})
         c == false && ((t_n, t_p) = (t, []))
+        append!(variants_params_unconstr[i], t_p)
         t_p_no_sup = [p isa Expr && p.head == :(<:) ? p.args[1] : p for p in t_p]
         push!(variants_types, t_p != [] ? :($t_n{$(t_p_no_sup...)}) : t_n)
         h_t = gensym(t_n)
@@ -44,13 +54,6 @@ macro sum_structs(type, struct_defs)
         struct_defs[i] = d_new
     end
 
-    fields_each, default_each = [], []
-    for a_spec in struct_defs
-        a_comps = decompose_struct_no_base(a_spec)
-        push!(fields_each, a_comps[2][1])
-        push!(default_each, a_comps[2][2])
-    end
-
     struct_defs = [:($Base.@kwdef $d) for d in struct_defs]
 
     variants_defs = [:($t(ht::$ht)) for (t, ht) in zip(variants_types, hidden_struct_types)]
@@ -139,22 +142,34 @@ macro sum_structs(type, struct_defs)
 
     expr_constructors = []
 
-    for (fs, fd, t, h_t, is_kw) in zip(fields_each, default_each, variants_types, hidden_struct_types, is_kws)
-        f_d_n = retrieve_fields_names(fs, false)
-        f_d_n_t = retrieve_fields_names(fs, true)
+    for (fs, fd, t, h_t, t_p_u, is_kw) in zip(fields_each, default_each, variants_types, hidden_struct_types, variants_params_unconstr, is_kws)
+        f_params_args = retrieve_fields_names(fs, false)
+        f_params_args_with_T = retrieve_fields_names(fs, true)
         c = @capture(t, t_n_{t_p__})
         a_spec_n_d = [d != "#328723329" ? Expr(:kw, n, d) : (:($n)) 
-                          for (n, d) in zip(f_d_n, fd)]
+                          for (n, d) in zip(f_params_args, fd)]
         f_params_kwargs = Expr(:parameters, a_spec_n_d...)
+        @capture(type, new_type_n_{new_type_p__})
+        if new_type_p === nothing 
+            new_type_n, new_type_p = type, []
+        end
+        new_type_p = [t isa Expr && t.head == :(<:) ? t.args[1] : t for t in new_type_p]
+        f_params_args_with_T = [!any(p -> inexpr(x, p), new_type_p) ? (x isa Symbol ? x : x.args[1]) : x 
+                                for x in f_params_args_with_T]
+        struct_spec_n2_d = [d != "#328723329" ? Expr(:kw, n, d) : (:($n)) 
+                      for (n, d) in zip(f_params_args_with_T, fd)]
+        f_params_kwargs_with_T = struct_spec_n2_d
+        f_params_kwargs_with_T = Expr(:parameters, f_params_kwargs_with_T...)
+
         if t_p !== nothing
-            c1 = :(function $t($(f_d_n...)) where {$(t_p...)}
-                       return $t($h_t($(f_d_n...)))
+            c1 = :(function $t($(f_params_args...)) where {$(t_p_u...)}
+                       return $t($h_t($(f_params_args...)))
                    end
                   )
             c4 = :()
             if is_kw
-                c4 = :(function $t($(f_params_kwargs)) where {$(t_p...)}
-                           return $t($h_t($(f_d_n...)))
+                c4 = :(function $t($(f_params_kwargs)) where {$(t_p_u...)}
+                           return $t($h_t($(f_params_args...)))
                        end
                       )
             end
@@ -162,14 +177,14 @@ macro sum_structs(type, struct_defs)
             c1 = :()
             c4 = :()
         end
-        c2 = :(function $(namify(t))($(f_d_n...))
-                   return $(namify(t))($(namify(h_t))($(f_d_n...)))
+        c2 = :(function $(namify(t))($(f_params_args_with_T...)) where {$(t_p_u...)}
+                   return $(namify(t))($(namify(h_t))($(f_params_args...)))
                end
               )
         c3 = :()
         if is_kw
-            c3 = :(function $(namify(t))($(f_params_kwargs))
-                       return $(namify(t))($(namify(h_t))($(f_d_n...)))
+            c3 = :(function $(namify(t))($(f_params_kwargs_with_T)) where {$(t_p_u...)}
+                       return $(namify(t))($(namify(h_t))($(f_params_args...)))
                    end
                   )
         end