diff --git a/activerecord/lib/active_record/associations/join_dependency/join_part.rb b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
index 2b1d888a9abd02ed6faca324050d3eae0e635283..711f7b3ce18bd9ea5653180c7214ce5b1e8772b5 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_part.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
@@ -54,7 +54,7 @@ def column_names_with_alias
           unless @column_names_with_alias
             @column_names_with_alias = []
 
-            ([primary_key] + (column_names - [primary_key])).each_with_index do |column_name, i|
+            ([primary_key] + (column_names - [primary_key])).compact.each_with_index do |column_name, i|
               @column_names_with_alias << [column_name, "#{aliased_prefix}_r#{i}"]
             end
           end
diff --git a/activerecord/test/cases/associations/join_dependency_test.rb b/activerecord/test/cases/associations/join_dependency_test.rb
new file mode 100644
index 0000000000000000000000000000000000000000..08c166dc33427064c8be96fa010cfdd836f14904
--- /dev/null
+++ b/activerecord/test/cases/associations/join_dependency_test.rb
@@ -0,0 +1,8 @@
+require "cases/helper"
+require 'models/edge'
+
+class JoinDependencyTest < ActiveRecord::TestCase
+  def test_column_names_with_alias_handles_nil_primary_key
+    assert_equal Edge.column_names, ActiveRecord::Associations::JoinDependency::JoinBase.new(Edge).column_names_with_alias.map(&:first)
+  end
+end
\ No newline at end of file