diff --git a/lib/rbs/collection/config/lockfile_generator.rb b/lib/rbs/collection/config/lockfile_generator.rb
index 371e9ee03..1f6575573 100644
--- a/lib/rbs/collection/config/lockfile_generator.rb
+++ b/lib/rbs/collection/config/lockfile_generator.rb
@@ -188,8 +188,8 @@ def generate
               lockfile.gems[name] = { name: name, version: "0", source: source }
             end
             return
-          when 'set', 'pathname'
-            # set and pathname is migrated to core from stdlib.
+          when 'set'
+            # set is migrated to core from stdlib.
             RBS.logger.info {
               from = from_gem || "rbs_collection.yaml"
               "`#{name}` is a part of the Ruby core library. The dependency to the library can be safely deleted from #{from}."
diff --git a/test/rbs/cli_test.rb b/test/rbs/cli_test.rb
index 278726dd0..9dc3b5925 100644
--- a/test/rbs/cli_test.rb
+++ b/test/rbs/cli_test.rb
@@ -1484,7 +1484,7 @@ def test_collection_install__pathname_set
         )
 
         assert_nil lockfile.gems["set"]
-        assert_nil lockfile.gems["pathname"]
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["pathname"][:source]
         assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["cgi-escape"][:source]
         assert_instance_of RBS::Collection::Sources::Git, lockfile.gems["ast"][:source]
       end
@@ -1517,7 +1517,6 @@ def test_collection_install__set_pathname__manifest
         _stdout, stderr = run_rbs_collection("install", bundler: true)
 
         assert_include stderr, '`set` is a part of the Ruby core library.'
-        assert_include stderr, '`pathname` is a part of the Ruby core library.'
 
         lockfile = RBS::Collection::Config::Lockfile.from_lockfile(
           lockfile_path: dir + "rbs_collection.lock.yaml",
@@ -1525,7 +1524,7 @@ def test_collection_install__set_pathname__manifest
         )
 
         assert_nil lockfile.gems["set"]
-        assert_nil lockfile.gems["pathname"]
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["pathname"][:source]
         assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["cgi-escape"][:source]
         assert_instance_of RBS::Collection::Sources::Local, lockfile.gems["true_string"][:source]
       end