diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/DefaultMemStore.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/DefaultMemStore.java
index 04a08bc8494..c0a4b51019f 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/DefaultMemStore.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/DefaultMemStore.java
@@ -292,6 +292,8 @@ public class DefaultMemStore implements MemStore {
     KeyValue found = this.snapshot.get(kv);
     if (found != null && found.getMvccVersion() == kv.getMvccVersion()) {
       this.snapshot.remove(kv);
+      long sz = heapSizeChange(kv, true);
+      this.snapshotSize -= sz;
     }
     // If the key is in the memstore, delete it. Update this.size.
     found = this.kvset.get(kv);
diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java
index 2334e8df28c..1edcba40601 100644
--- a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java
+++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java
@@ -116,6 +116,7 @@ import org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor
 import org.apache.hadoop.hbase.regionserver.HRegion.RegionScannerImpl;
 import org.apache.hadoop.hbase.regionserver.HRegion.RowLock;
 import org.apache.hadoop.hbase.regionserver.TestStore.FaultyFileSystem;
+import org.apache.hadoop.hbase.regionserver.wal.FaultyHLog;
 import org.apache.hadoop.hbase.regionserver.wal.HLog;
 import org.apache.hadoop.hbase.regionserver.wal.HLogFactory;
 import org.apache.hadoop.hbase.regionserver.wal.HLogKey;
@@ -234,6 +235,58 @@ public class TestHRegion {
     HRegion.closeHRegion(region);
   }
 
+  /*
+   * This test is for verifying memstore snapshot size is correctly updated in case of rollback
+   * See HBASE-10845
+   */
+  @Test (timeout=60000)
+  public void testMemstoreSnapshotSize() throws IOException {
+    class MyFaultyHLog extends FaultyHLog {
+      StoreFlushContext storeFlushCtx;
+      public MyFaultyHLog(FileSystem fs, Path rootDir, String logName, Configuration conf)
+          throws IOException {
+        super(fs, rootDir, logName, conf);
+      }
+      
+      void setStoreFlushCtx(StoreFlushContext storeFlushCtx) {
+        this.storeFlushCtx = storeFlushCtx;
+      }
+
+      @Override
+      public void sync(long txid) throws IOException {
+        storeFlushCtx.prepare();
+        super.sync(txid);
+      }
+    }
+    
+    FileSystem fs = FileSystem.get(CONF);
+    Path rootDir = new Path(dir + "testMemstoreSnapshotSize");
+    MyFaultyHLog faultyLog = new MyFaultyHLog(fs, rootDir, "testMemstoreSnapshotSize", CONF);
+    HRegion region = initHRegion(tableName, null, null, name.getMethodName(),
+      CONF, false, Durability.SYNC_WAL, faultyLog, COLUMN_FAMILY_BYTES);
+    
+    Store store = region.getStore(COLUMN_FAMILY_BYTES);
+    // Get some random bytes.
+    byte [] value = Bytes.toBytes(name.getMethodName());
+    faultyLog.setStoreFlushCtx(store.createFlushContext(12345));
+    
+    Put put = new Put(value);
+    put.add(COLUMN_FAMILY_BYTES, Bytes.toBytes("abc"), value);
+    faultyLog.setFailureType(FaultyHLog.FailureType.SYNC);
+
+    boolean threwIOE = false;
+    try {
+      region.put(put);
+    } catch (IOException ioe) {
+      threwIOE = true;
+    } finally {
+      assertTrue("The regionserver should have thrown an exception", threwIOE);
+    }
+    long sz = store.getFlushableSize();
+    assertTrue("flushable size should be zero, but it is " + sz, sz == 0);
+    HRegion.closeHRegion(region);
+  }
+  
   /**
    * Test we do not lose data if we fail a flush and then close.
    * Part of HBase-10466.  Tests the following from the issue description:
diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/FaultyHLog.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/FaultyHLog.java
new file mode 100644
index 00000000000..10ba82faaec
--- /dev/null
+++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/FaultyHLog.java
@@ -0,0 +1,70 @@
+/**
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.regionserver.wal;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HRegionInfo;
+import org.apache.hadoop.hbase.HTableDescriptor;
+import org.apache.hadoop.hbase.TableName;
+
+/*
+ * This is a utility class, used by tests, which fails operation specified by FailureType enum
+ */
+public class FaultyHLog extends FSHLog {
+  public enum FailureType {
+    NONE, APPENDNOSYNC, SYNC
+  }
+  FailureType ft = FailureType.NONE;
+
+  public FaultyHLog(FileSystem fs, Path rootDir, String logName, Configuration conf)
+      throws IOException {
+    super(fs, rootDir, logName, conf);
+  }
+  
+  public void setFailureType(FailureType fType) {
+    this.ft = fType;
+  }
+  
+  @Override
+  public void sync(long txid) throws IOException {
+    if (this.ft == FailureType.SYNC) {
+      throw new IOException("sync");
+    }
+    super.sync(txid);
+  }
+  @Override
+  public long appendNoSync(HRegionInfo info, TableName tableName, WALEdit edits,
+      List<UUID> clusterIds, final long now, HTableDescriptor htd, AtomicLong sequenceId,
+      boolean isInMemstore, long nonceGroup, long nonce) throws IOException {
+    if (this.ft == FailureType.APPENDNOSYNC) {
+      throw new IOException("appendNoSync");
+    }
+    return super.appendNoSync(info, tableName, edits, clusterIds, now, htd, sequenceId,
+      isInMemstore, nonceGroup, nonce);
+  }
+}
+