diff --git a/tests/project_helpers.py b/tests/project_helpers.py
index 83c4ba2c..0a467ece 100644
--- a/tests/project_helpers.py
+++ b/tests/project_helpers.py
@@ -146,7 +146,7 @@ def venv_script_lines(self, venv_path: Path) -> List[str]:
                 for req in self.requirements
             ]
             + [
-                f"{create_empty_file} {venv_path}/.installed",
+                f"{create_empty_file} {venv_path / '.installed'}",
             ]
         )
 
diff --git a/tests/test_real_projects.py b/tests/test_real_projects.py
index 0eafb8ee..f782f3da 100644
--- a/tests/test_real_projects.py
+++ b/tests/test_real_projects.py
@@ -7,7 +7,9 @@
 """
 import json
 import logging
+import os
 import subprocess
+import sys
 import tarfile
 from dataclasses import dataclass
 from pathlib import Path
@@ -51,7 +53,7 @@ def verify_requirements(venv_path: Path, requirements: List[str]) -> None:
 def run_fawltydeps_json(
     *args: str, venv_dir: Optional[Path], cwd: Optional[Path] = None
 ) -> JsonData:
-    argv = ["fawltydeps", "--config-file=/dev/null", "--json"]
+    argv = [sys.executable, "-m", "fawltydeps", f"--config-file={os.devnull}", "--json"]
     if venv_dir is not None:
         argv += [f"--pyenv={venv_dir}"]
     proc = subprocess.run(