diff --git a/pkg/cache.go b/pkg/cache.go
index ba18a8e..83dd835 100644
--- a/pkg/cache.go
+++ b/pkg/cache.go
@@ -68,7 +68,7 @@ func SaveCache(newCache *LocalCache) {
 
 	tmpfile, err := os.CreateTemp("", "stakefish-eth2-monitor-cache.*.json")
 	if err != nil {
-		log.Debug().Err(err).Msg("SaveCache: os.Open failed; skip")
+		log.Warn().Err(err).Msg("SaveCache: os.CreateTemp failed; skip")
 		return
 	}
 	defer os.Remove(tmpfile.Name())
diff --git a/pkg/monitoring.go b/pkg/monitoring.go
index 6b997b5..5814de5 100644
--- a/pkg/monitoring.go
+++ b/pkg/monitoring.go
@@ -353,6 +353,7 @@ func MonitorAttestationsAndProposals(ctx context.Context, beacon *beaconchain.Be
 		})
 	prometheus.MustRegister(totalDelayedAttestationsOverToleranceCounter)
 
+	// https://www.attestant.io/posts/defining-attestation-effectiveness/
 	canonicalAttestationDistances := prometheus.NewHistogram(prometheus.HistogramOpts{
 		Namespace: "ETH2",
 		Name:      "canonicalAttestationDistances",
@@ -477,9 +478,11 @@ func MonitorAttestationsAndProposals(ctx context.Context, beacon *beaconchain.Be
 						continue
 					}
 
-					attestationDistance := blockSlot - phase0.Slot(attestedSlot)
-					// Take skipped slots into account
-					for s := attestedSlot; s < uint64(blockSlot); s++ {
+					// https://www.attestant.io/posts/defining-attestation-effectiveness/
+					earliestInclusionSlot := attestedSlot + 1
+					attestationDistance := blockSlot - phase0.Slot(earliestInclusionSlot)
+					// Do not penalize validator for skipped slots
+					for s := earliestInclusionSlot; s < uint64(blockSlot); s++ {
 						if _, ok := epochBlocks[s]; !ok {
 							attestationDistance--
 						}