diff --git a/source/blender/makesrna/intern/makesrna.cc b/source/blender/makesrna/intern/makesrna.cc
index 719898b821b..e66c23f9e0a 100644
--- a/source/blender/makesrna/intern/makesrna.cc
+++ b/source/blender/makesrna/intern/makesrna.cc
@@ -2180,6 +2180,17 @@ static void rna_def_property_funcs(FILE *f, StructRNA *srna, PropertyDefRNA *dp)
     case PROP_ENUM: {
       EnumPropertyRNA *eprop = (EnumPropertyRNA *)prop;
 
+      if (dp->enumbitflags && eprop->item_fn &&
+          !(eprop->item != rna_enum_dummy_NULL_items || eprop->set || eprop->set_ex))
+      {
+        CLOG_ERROR(&LOG,
+                   "%s.%s, bitflag enum should not define an `item` callback function, unless "
+                   "they also define a static list of items, or a custom `set` callback.",
+                   srna->identifier,
+                   prop->identifier);
+        DefRNA.error = true;
+      }
+
       if (!(prop->flag & PROP_EDITABLE) && (eprop->set || eprop->set_ex)) {
         CLOG_ERROR(&LOG,
                    "%s.%s, is read-only but has defines a \"set\" callback.",
@@ -4210,10 +4221,11 @@ static void rna_generate_property(FILE *f, StructRNA *srna, const char *nest, Pr
         else {
           if (!defaultfound && !(eprop->item_fn && eprop->item == rna_enum_dummy_NULL_items)) {
             CLOG_ERROR(&LOG,
-                       "%s%s.%s, enum default is not in items.",
+                       "%s%s.%s, enum default '%d' is not in items.",
                        srna->identifier,
                        errnest,
-                       prop->identifier);
+                       prop->identifier,
+                       eprop->defaultvalue);
             DefRNA.error = true;
           }
         }
diff --git a/source/blender/makesrna/intern/rna_define.cc b/source/blender/makesrna/intern/rna_define.cc
index d5d524e5916..69ecabc8291 100644
--- a/source/blender/makesrna/intern/rna_define.cc
+++ b/source/blender/makesrna/intern/rna_define.cc
@@ -2965,17 +2965,6 @@ void RNA_def_property_enum_bitflag_sdna(PropertyRNA *prop,
 
   if (dp) {
     dp->enumbitflags = 1;
-
-#ifndef RNA_RUNTIME
-    int defaultvalue_mask = 0;
-    EnumPropertyRNA *eprop = (EnumPropertyRNA *)prop;
-    for (int i = 0; i < eprop->totitem; i++) {
-      if (eprop->item[i].identifier[0]) {
-        defaultvalue_mask |= eprop->defaultvalue & eprop->item[i].value;
-      }
-    }
-    eprop->defaultvalue = defaultvalue_mask;
-#endif
   }
 }
 
diff --git a/source/blender/makesrna/intern/rna_userdef.cc b/source/blender/makesrna/intern/rna_userdef.cc
index 9dc3889e3d0..a8b4918372b 100644
--- a/source/blender/makesrna/intern/rna_userdef.cc
+++ b/source/blender/makesrna/intern/rna_userdef.cc
@@ -5371,6 +5371,7 @@ static void rna_def_userdef_view(BlenderRNA *brna)
   prop = RNA_def_property(srna, "header_align", PROP_ENUM, PROP_NONE);
   RNA_def_property_enum_items(prop, header_align_items);
   RNA_def_property_enum_bitflag_sdna(prop, nullptr, "uiflag");
+  RNA_def_property_enum_default(prop, USER_HEADER_FROM_PREF | USER_HEADER_BOTTOM);
   RNA_def_property_ui_text(prop, "Header Position", "Default header position for new space-types");
   RNA_def_property_update(prop, 0, "rna_userdef_screen_update_header_default");