diff --git a/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCache.java b/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCache.java
index a914c876..5220c6ae 100644
--- a/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCache.java
+++ b/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCache.java
@@ -36,7 +36,9 @@ public class BlockingGetRecordsCache implements GetRecordsCache {
 
     @Override
     public void start() {
-        // Do nothing, this behavior is not supported by this cache.
+        //
+        // Nothing to do here
+        //
     }
 
     @Override
@@ -50,6 +52,8 @@ public class BlockingGetRecordsCache implements GetRecordsCache {
 
     @Override
     public void shutdown() {
+        //
         // Nothing to do here.
+        //
     }
 }
diff --git a/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/PrefetchGetRecordsCache.java b/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/PrefetchGetRecordsCache.java
index 625cd611..f5d82dab 100644
--- a/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/PrefetchGetRecordsCache.java
+++ b/src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/PrefetchGetRecordsCache.java
@@ -116,15 +116,15 @@ public class PrefetchGetRecordsCache implements GetRecordsCache {
     }
 
     private class PrefetchCounters {
-        private volatile long size = 0;
-        private volatile long byteSize = 0;
+        private long size = 0;
+        private long byteSize = 0;
 
-        public void added(final ProcessRecordsInput result) {
+        public synchronized void added(final ProcessRecordsInput result) {
             size += getSize(result);
             byteSize += getByteSize(result);
         }
 
-        public void removed(final ProcessRecordsInput result) {
+        public synchronized void removed(final ProcessRecordsInput result) {
             size -= getSize(result);
             byteSize -= getByteSize(result);
         }
diff --git a/src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCacheTest.java b/src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCacheTest.java
index 67afe09e..dbe9d843 100644
--- a/src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCacheTest.java
+++ b/src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/BlockingGetRecordsCacheTest.java
@@ -21,6 +21,7 @@ import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.when;
 
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.List;
 
 import org.junit.Before;
@@ -44,9 +45,8 @@ public class BlockingGetRecordsCacheTest {
     private GetRecordsRetrievalStrategy getRecordsRetrievalStrategy;
     @Mock
     private GetRecordsResult getRecordsResult;
-    @Mock
-    private List<Record> records;
-
+    
+    private List<Record> records = new ArrayList<>();
     private BlockingGetRecordsCache blockingGetRecordsCache;
 
     @Before
@@ -58,7 +58,7 @@ public class BlockingGetRecordsCacheTest {
     }
 
     @Test
-    public void testGetNextRecords() {
+    public void testGetNextRecordsWithNoRecords() {
         ProcessRecordsInput result = blockingGetRecordsCache.getNextResult();
 
         assertEquals(result.getRecords(), records);
@@ -66,4 +66,17 @@ public class BlockingGetRecordsCacheTest {
         assertNull(result.getCacheExitTime());
         assertEquals(result.getTimeSpentInCache(), Duration.ZERO);
     }
+    
+    @Test
+    public void testGetNextRecordsWithRecords() {
+        Record record = new Record();
+        records.add(record);
+        records.add(record);
+        records.add(record);
+        records.add(record);
+        
+        ProcessRecordsInput result = blockingGetRecordsCache.getNextResult();
+        
+        assertEquals(result.getRecords(), records);
+    }
 }