diff --git a/scripts/docs/generate-diagrams.py b/scripts/docs/generate-diagrams.py
index 637ca67..a2b2547 100644
--- a/scripts/docs/generate-diagrams.py
+++ b/scripts/docs/generate-diagrams.py
@@ -153,10 +153,11 @@ def generate_physical_topology(compose: dict, inventory: dict, out_dot: Path, ou
         else:
             orphans.append(vm)
     for host, record in sorted(phys_names.items()):
-        host_role = record.get("role", "")
+        host_role = str(record.get("role", "") or "")
+        cluster_label = f"{host}\\n{host_role}" if host_role else host
         lines.extend([
             f'  subgraph "cluster_{host}" {{',
-            f'    label="{host}\\n{host_role}".strip();',
+            f'    label="{cluster_label}";',
             '    style="rounded,filled";',
             '    color="#60a5fa";',
             '    fillcolor="#eff6ff";',