diff --git a/src/dump.c b/src/dump.c
index 84a84032f4aa4..1105e375b17bc 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -257,7 +257,7 @@ static int type_parameter_recursively_external(jl_value_t *p0) JL_NOTSAFEPOINT
         return 0;
     if (module_in_worklist(p->name->module))
         return 0;
-    if (jl_unwrap_unionall(p->name->wrapper) != (jl_value_t*)p) {
+    if (p->name->wrapper != (jl_value_t*)p0) {
         if (!type_recursively_external(p))
             return 0;
     }
@@ -327,11 +327,8 @@ static void jl_serialize_datatype(jl_serializer_state *s, jl_datatype_t *dt) JL_
 
     write_uint8(s->s, TAG_DATATYPE);
     write_uint8(s->s, tag);
-    if (tag == 6) {
-        jl_serialize_value(s, dt->name);
-        return;
-    }
-    if (tag == 7) {
+    if (tag == 6 || tag == 7) {
+        // for tag==6, copy its typevars in case there are references to them elsewhere
         jl_serialize_value(s, dt->name);
         jl_serialize_value(s, dt->parameters);
         return;
@@ -745,7 +742,7 @@ static void jl_serialize_value_(jl_serializer_state *s, jl_value_t *v, int as_li
     else if (jl_is_unionall(v)) {
         write_uint8(s->s, TAG_UNIONALL);
         jl_datatype_t *d = (jl_datatype_t*)jl_unwrap_unionall(v);
-        if (jl_is_datatype(d) && jl_unwrap_unionall(d->name->wrapper) == (jl_value_t*)d &&
+        if (jl_is_datatype(d) && d->name->wrapper == v &&
             !module_in_worklist(d->name->module)) {
             write_uint8(s->s, 1);
             jl_serialize_value(s, d->name->module);
@@ -1335,13 +1332,8 @@ static jl_value_t *jl_deserialize_datatype(jl_serializer_state *s, int pos, jl_v
     if (tag == 6 || tag == 7) {
         jl_typename_t *name = (jl_typename_t*)jl_deserialize_value(s, NULL);
         jl_value_t *dtv = name->wrapper;
-        if (tag == 7) {
-            jl_svec_t *parameters = (jl_svec_t*)jl_deserialize_value(s, NULL);
-            dtv = jl_apply_type(dtv, jl_svec_data(parameters), jl_svec_len(parameters));
-        }
-        else {
-            dtv = jl_unwrap_unionall(dtv);
-        }
+        jl_svec_t *parameters = (jl_svec_t*)jl_deserialize_value(s, NULL);
+        dtv = jl_apply_type(dtv, jl_svec_data(parameters), jl_svec_len(parameters));
         backref_list.items[pos] = dtv;
         return dtv;
     }
diff --git a/test/precompile.jl b/test/precompile.jl
index ed93b60bfdd4f..c8f502b8b58b5 100644
--- a/test/precompile.jl
+++ b/test/precompile.jl
@@ -135,6 +135,8 @@ try
 
               const x28297 = Result(missing)
 
+              const d29936a = UnionAll(Dict.var, UnionAll(Dict.body.var, Dict.body.body))
+              const d29936b = UnionAll(Dict.body.var, UnionAll(Dict.var, Dict.body.body))
 
               # issue #28998
               const x28998 = [missing, 2, missing, 6, missing,
@@ -187,6 +189,9 @@ try
 
         @test Foo.x28297.result === missing
 
+        @test Foo.d29936a === Dict
+        @test Foo.d29936b === Dict{K,V} where {V,K}
+
         @test Foo.x28998[end] == 6
     end