diff --git a/lib/ldclient-rb/user_filter.rb b/lib/ldclient-rb/user_filter.rb
index 8cbf67ca..b67f6844 100644
--- a/lib/ldclient-rb/user_filter.rb
+++ b/lib/ldclient-rb/user_filter.rb
@@ -15,8 +15,9 @@ def transform_user_props(user_props)
       user_private_attrs = Set.new((user_props[:privateAttributeNames] || []).map(&:to_sym))
 
       filtered_user_props, removed = filter_values(user_props, user_private_attrs, ALLOWED_TOP_LEVEL_KEYS, IGNORED_TOP_LEVEL_KEYS)
-      if user_props.has_key?(:custom)
-        filtered_user_props[:custom], removed_custom = filter_values(user_props[:custom], user_private_attrs)
+      custom = user_props[:custom]
+      if !custom.nil?
+        filtered_user_props[:custom], removed_custom = filter_values(custom, user_private_attrs)
         removed.merge(removed_custom)
       end
 
diff --git a/spec/events_spec.rb b/spec/events_spec.rb
index c32eeb29..d7854567 100644
--- a/spec/events_spec.rb
+++ b/spec/events_spec.rb
@@ -408,6 +408,17 @@ def with_processor_and_sender(config)
     end
   end
 
+  it "treats nil value for custom the same as an empty hash" do
+    with_processor_and_sender(default_config) do |ep, sender|
+      user_with_nil_custom = { key: "userkey", custom: nil }
+      e = { kind: "identify", key: "userkey", user: user_with_nil_custom }
+      ep.add_event(e)
+
+      output = flush_and_get_events(ep, sender)
+      expect(output).to contain_exactly(e)
+    end
+  end
+
   it "does a final flush when shutting down" do
     with_processor_and_sender(default_config) do |ep, sender|
       e = { kind: "identify", key: user[:key], user: user }