diff --git a/src/datatype.c b/src/datatype.c
index 63069f3675854..908a9a457d05b 100644
--- a/src/datatype.c
+++ b/src/datatype.c
@@ -770,7 +770,16 @@ JL_DLLEXPORT jl_value_t *jl_new_structv(jl_datatype_t *type, jl_value_t **args,
                                         uint32_t na)
 {
     jl_ptls_t ptls = jl_get_ptls_states();
-    if (type->instance != NULL) return type->instance;
+    if (type->instance != NULL) {
+        for (size_t i = 0; i < na; i++) {
+            jl_value_t *ft = jl_field_type(type, i);
+            if (!jl_isa(args[i], ft))
+                jl_type_error("new", ft, args[i]);
+        }
+        return type->instance;
+    }
+    if (type->layout == NULL)
+        jl_type_error("new", (jl_value_t*)jl_datatype_type, (jl_value_t*)type);
     size_t nf = jl_datatype_nfields(type);
     jl_value_t *jv = jl_gc_alloc(ptls, jl_datatype_size(type), type);
     JL_GC_PUSH1(&jv);
@@ -783,8 +792,8 @@ JL_DLLEXPORT jl_value_t *jl_new_structv(jl_datatype_t *type, jl_value_t **args,
     for(size_t i=na; i < nf; i++) {
         if (jl_field_isptr(type, i)) {
             *(jl_value_t**)((char*)jl_data_ptr(jv)+jl_field_offset(type,i)) = NULL;
-
-        } else {
+        }
+        else {
             jl_value_t *ft = jl_field_type(type, i);
             if (jl_is_uniontype(ft)) {
                 uint8_t *psel = &((uint8_t *)jv)[jl_field_offset(type, i) + jl_field_size(type, i) - 1];
diff --git a/src/interpreter.c b/src/interpreter.c
index 61d803cbf043a..feb0bbbe168a4 100644
--- a/src/interpreter.c
+++ b/src/interpreter.c
@@ -477,18 +477,12 @@ SECT_INTERP static jl_value_t *eval_value(jl_value_t *e, interpreter_state *s)
         return jl_nothing;
     }
     else if (head == new_sym) {
-        jl_value_t *thetype = eval_value(args[0], s);
-        jl_value_t *v=NULL, *fldv=NULL;
-        JL_GC_PUSH3(&thetype, &v, &fldv);
-        assert(jl_is_structtype(thetype));
-        v = jl_new_struct_uninit((jl_datatype_t*)thetype);
-        for (size_t i = 1; i < nargs; i++) {
-            jl_value_t *ft = jl_field_type(thetype, i - 1);
-            fldv = eval_value(args[i], s);
-            if (!jl_isa(fldv, ft))
-                jl_type_error("new", ft, fldv);
-            jl_set_nth_field(v, i - 1, fldv);
-        }
+        jl_value_t **argv;
+        JL_GC_PUSHARGS(argv, nargs);
+        for (size_t i = 0; i < nargs; i++)
+            argv[i] = eval_value(args[i], s);
+        assert(jl_is_structtype(argv[0]));
+        jl_value_t *v = jl_new_structv((jl_datatype_t*)argv[0], &argv[1], nargs - 1);
         JL_GC_POP();
         return v;
     }
diff --git a/test/core.jl b/test/core.jl
index ff9282a243b40..f1e4112c86677 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -6702,3 +6702,11 @@ end
 @test_throws ErrorException Array{Int, 2}(undef, 0, -10)
 @test_throws ErrorException Array{Int, 2}(undef, -10, 0)
 @test_throws ErrorException Array{Int, 2}(undef, -1, -1)
+
+# issue #29145
+struct T29145{A,B}
+    function T29145()
+        new{S,Ref{S}}() where S
+    end
+end
+@test_throws TypeError T29145()