diff --git a/app/models/person.rb b/app/models/person.rb
index 819e930da4c..f32055834b7 100644
--- a/app/models/person.rb
+++ b/app/models/person.rb
@@ -278,6 +278,14 @@ def self.fields_edit_requestable
     methods: ["url", "country_iso2"],
   }.freeze
 
+  USER_COMMON_SERIALIZE_OPTIONS = {
+    only: ["name", "gender"],
+    methods: ["country_iso2"],
+    # grrr… some tests (and apparently also API endpoints) rely on serializing this data _through_ person.
+    #   Not a good code design decision, but very cumbersome to properly refactor. Signed GB 2025-01-09
+    include: User::DEFAULT_SERIALIZE_OPTIONS[:include],
+  }.freeze
+
   def personal_records
     [self.ranksAverage, self.ranksSingle].compact.flatten
   end
@@ -306,8 +314,17 @@ def serializable_hash(options = nil)
       json[:incorrect_wca_id_claim_count] = incorrect_wca_id_claim_count
     end
 
+    # Passing down options from Person to User (which are completely different models in the DB!)
+    #   is a horrible idea. Unfortunately, our external APIs have come to rely on it,
+    #   so we need to hack around it.
+    #   - `merge_union` makes sure that only values specified in USER_COMMON_SERIALIZE_OPTIONS kick in
+    #   - `filter` makes sure that when the result of `merge_union` are empty, the defaults from
+    #       User::DEFAULT_SERIALIZE_OPTIONS can override.
+    user_override_options = USER_COMMON_SERIALIZE_OPTIONS.merge_union(options&.stringify_keys)
+                                                         .filter { |_, v| v.present? }
+
     # If there's a user for this Person, merge in all their data,
     # the Person's data takes priority, though.
-    (user || User.new).serializable_hash(options).merge(json)
+    (user || User.new).serializable_hash(user_override_options).merge(json)
   end
 end
diff --git a/config/initializers/monkey_patches.rb b/config/initializers/monkey_patches.rb
index b0ec1cd5b41..003ccbe9aba 100644
--- a/config/initializers/monkey_patches.rb
+++ b/config/initializers/monkey_patches.rb
@@ -51,6 +51,14 @@ def xss_aware_join(delimiter = '')
     end
   end
 
+  Hash.class_eval do
+    def merge_union(other = nil)
+      self.to_h do |key, value|
+        [key, value & (other&.fetch(key.to_s, []) || [])]
+      end
+    end
+  end
+
   ActiveSupport::Duration.class_eval do
     def in_seconds
       self.to_i