diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java
index aa0dd7c..9ca5494 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java
@@ -86,7 +86,7 @@
     }
 
     @Override
-    public List<Long> appendEntries(List<Entry> entries) {
+    public synchronized List<Long> appendEntries(List<Entry> entries) {
         assertIsOpen();
         checkArgument(entries != null, "expecting non-null entries");
         final List<Long> indices = new ArrayList<>(entries.size());