diff --git a/scripts/integration-vm.py b/scripts/integration-vm.py
index aa96291..d71c781 100644
--- a/scripts/integration-vm.py
+++ b/scripts/integration-vm.py
@@ -44,6 +44,11 @@ DEFAULT_VCPUS = 2
 MIN_FREE_MIB = 4096
 VALID_TIERS = ("internal", "le-staging", "le-prod-wildcard")
 
+# Target the SYSTEM libvirtd — where the substrate, /dev/kvm, and the NAT network live.
+# Without this, a non-root caller's bare virsh/virt-install default to qemu:///session.
+os.environ.setdefault("LIBVIRT_DEFAULT_URI", "qemu:///system")
+
+
 def vm_name(host, suffix=None):
     suffix = suffix or uuid.uuid4().hex[:8]
     return f"{NAME_PREFIX}{host}-{suffix}"