diff --git a/osbuild/buildroot.py b/osbuild/buildroot.py
index b99d256c..baa2b960 100644
--- a/osbuild/buildroot.py
+++ b/osbuild/buildroot.py
@@ -113,7 +113,7 @@ class BuildRoot(contextlib.AbstractContextManager):
             "--as-pid2",
             "--link-journal=no",
             f"--directory={self.root}",
-            f"--setenv=PYTHONPATH=/run/osbuild/lib",
+            "--setenv=PYTHONPATH=/run/osbuild/lib",
             *[f"--bind-ro={b}" for b in nspawn_ro_binds],
             *[f"--bind={b}" for b in (binds or [])],
             *[f"--bind-ro={b}" for b in (readonly_binds or [])],