diff --git a/invoice/src/main/java/org/killbill/billing/invoice/usage/RawUsageOptimizer.java b/invoice/src/main/java/org/killbill/billing/invoice/usage/RawUsageOptimizer.java
index b33ffb3..06c591a 100644
--- a/invoice/src/main/java/org/killbill/billing/invoice/usage/RawUsageOptimizer.java
+++ b/invoice/src/main/java/org/killbill/billing/invoice/usage/RawUsageOptimizer.java
@@ -43,7 +43,6 @@ import org.slf4j.LoggerFactory;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
-import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Ordering;
@@ -120,9 +119,11 @@ public class RawUsageOptimizer {
final ListIterator<InvoiceItem> iterator = sortedUsageItems.listIterator(sortedUsageItems.size());
while (iterator.hasPrevious()) {
- final InvoiceItem previous = iterator.previous();
- Preconditions.checkState(previous instanceof UsageInvoiceItem);
- final UsageInvoiceItem item = (UsageInvoiceItem) previous;
+ final InvoiceItem item = iterator.previous();
+ if (!(item instanceof UsageInvoiceItem)) {
+ // Help to debug https://github.com/killbill/killbill/issues/1095
+ log.warn("RawUsageOptimizer : item id={}, expected to see an UsageInvoiceItem type, got {}", item.getId(), item);
+ }
final Usage usage = knownUsage.get(item.getUsageName());
if (perBillingPeriodMostRecentConsumableInArrearItemEndDate[usage.getBillingPeriod().ordinal()] == null) {
