diff --git a/scripts/lib/env.py b/scripts/lib/env.py
index 58042e5..f5b61d7 100644
--- a/scripts/lib/env.py
+++ b/scripts/lib/env.py
@@ -264,7 +264,7 @@ def get_config() -> dict[str, Any]:
         ('XQUIK_API_KEY', None),
         ('FROM_BROWSER', None),
         ('SETUP_COMPLETE', None),
-        ('INCLUDE_SOURCES', None),
+        ('INCLUDE_SOURCES', ''),
     ]
 
     for key, default in keys:
diff --git a/tests/test_env_include_sources_default.py b/tests/test_env_include_sources_default.py
new file mode 100644
index 0000000..a6e2bfd
--- /dev/null
+++ b/tests/test_env_include_sources_default.py
@@ -0,0 +1,14 @@
+from scripts.lib import env
+
+
+def test_include_sources_defaults_to_empty_string(monkeypatch, tmp_path):
+    # Ensure the env var is not set
+    monkeypatch.delenv("INCLUDE_SOURCES", raising=False)
+
+    # Avoid reading any real user config file by patching the resolved module path directly
+    monkeypatch.setattr(env, "CONFIG_FILE", tmp_path / "does-not-exist.env")
+
+    cfg = env.get_config()
+
+    assert "INCLUDE_SOURCES" in cfg
+    assert cfg["INCLUDE_SOURCES"] == ""