diff --git a/platformio/managers/package.py b/platformio/managers/package.py
index fd8b0393..d66cb1f9 100644
--- a/platformio/managers/package.py
+++ b/platformio/managers/package.py
@@ -553,7 +553,8 @@ class BasePkgManager(PkgRepoMixin, PkgInstallerMixin):
         `False` - package is up-to-date
         `String` - a found latest version
         """
-        assert isdir(pkg_dir)
+        if not isdir(pkg_dir):
+            return None
         latest = None
         manifest = self.load_manifest(pkg_dir)
         # skip fixed package to a specific version
diff --git a/tests/commands/test_lib.py b/tests/commands/test_lib.py
index 31ed9809..02eac43b 100644
--- a/tests/commands/test_lib.py
+++ b/tests/commands/test_lib.py
@@ -184,7 +184,7 @@ def test_global_lib_update(clirunner, validate_cliresult, isolated_pio_home):
     result = clirunner.invoke(cmd_lib, ["-g", "update"])
     validate_cliresult(result)
     validate_cliresult(result)
-    assert result.output.count("[Skip]") == 5
+    assert result.output.count("[Fixed]") == 5
     assert result.output.count("[Up-to-date]") == 10
     assert "Uninstalling ArduinoJson @ 5.7.3" in result.output
     assert "Uninstalling IRremoteESP8266 @ fee16e880b" in result.output