diff --git a/src/lean_spec/node/metrics/spec_observer.py b/src/lean_spec/node/metrics/spec_observer.py
index 289eb8bde..603e02b3d 100644
--- a/src/lean_spec/node/metrics/spec_observer.py
+++ b/src/lean_spec/node/metrics/spec_observer.py
@@ -11,9 +11,10 @@
 from __future__ import annotations
 
 from lean_spec.node.metrics.registry import registry as metrics
+from lean_spec.spec.observability.observer import SpecObserver
 
 
-class PrometheusObserver:
+class PrometheusObserver(SpecObserver):
     """Forward SpecObserver callbacks to Prometheus metrics."""
 
     def state_transition_timed(self, seconds: float) -> None: