diff --git a/tests/unit/test_config.py b/tests/unit/test_config.py
index 68434a7..5803a17 100644
--- a/tests/unit/test_config.py
+++ b/tests/unit/test_config.py
@@ -12,7 +12,6 @@ from devx.config import (
     TASK_ID_RE,
     TASK_PREFIX,
     VIKUNJA_API_URL,
-    VIKUNJA_PROJECT_ID,
 )
 
 
@@ -21,8 +20,17 @@ class TestConfigConstants:
         assert "api/v1" in GITEA_API_URL
         assert "api/v1" in VIKUNJA_API_URL
 
-    def test_project_ids(self) -> None:
-        assert VIKUNJA_PROJECT_ID == 6
+    def test_project_ids(self, monkeypatch: object) -> None:
+        """VIKUNJA_PROJECT_ID defaults to 6 when DEVX_VIKUNJA_PROJECT_ID is not set."""
+        monkeypatch.delenv("DEVX_VIKUNJA_PROJECT_ID", raising=False)
+        import importlib
+
+        import devx.config as cfg
+
+        importlib.reload(cfg)
+        assert cfg.VIKUNJA_PROJECT_ID == 6
+        # Restore module state
+        importlib.reload(cfg)
 
     def test_timeouts(self) -> None:
         assert DEFAULT_TIMEOUT == 30