diff --git a/src/java/org/apache/lucene/store/RAMFile.java b/src/java/org/apache/lucene/store/RAMFile.java
index 4d2eb7ba115..99736af9440 100644
--- a/src/java/org/apache/lucene/store/RAMFile.java
+++ b/src/java/org/apache/lucene/store/RAMFile.java
@@ -24,8 +24,7 @@ class RAMFile implements Serializable {
 
   private static final long serialVersionUID = 1l;
 
-  // Direct read-only access to state supported for streams since a writing stream implies no other concurrent streams
-  ArrayList buffers = new ArrayList();
+  private ArrayList buffers = new ArrayList();
   long length;
   RAMDirectory directory;
   long sizeInBytes;                  // Only maintained if in a directory; updates synchronized on directory
@@ -58,8 +57,7 @@ class RAMFile implements Serializable {
     this.lastModified = lastModified;
   }
 
-  // Only one writing stream with no concurrent reading streams, so no file synchronization required
-  final byte[] addBuffer(int size) {
+  final synchronized byte[] addBuffer(int size) {
     byte[] buffer = newBuffer(size);
     if (directory!=null)
       synchronized (directory) {             // Ensure addition of buffer and adjustment to directory size are atomic wrt directory
@@ -72,6 +70,14 @@ class RAMFile implements Serializable {
     return buffer;
   }
 
+  final synchronized byte[] getBuffer(int index) {
+    return (byte[]) buffers.get(index);
+  }
+
+  final synchronized int numBuffers() {
+    return buffers.size();
+  }
+
   /**
    * Expert: allocate a new buffer. 
    * Subclasses can allocate differently. 
diff --git a/src/java/org/apache/lucene/store/RAMInputStream.java b/src/java/org/apache/lucene/store/RAMInputStream.java
index 7e9a54ba165..c2a3a72ce3d 100644
--- a/src/java/org/apache/lucene/store/RAMInputStream.java
+++ b/src/java/org/apache/lucene/store/RAMInputStream.java
@@ -84,11 +84,11 @@ class RAMInputStream extends IndexInput implements Cloneable {
   }
 
   private final void switchCurrentBuffer() throws IOException {
-    if (currentBufferIndex >= file.buffers.size()) {
+    if (currentBufferIndex >= file.numBuffers()) {
       // end of file reached, no more buffers left
       throw new IOException("Read past EOF");
     } else {
-      currentBuffer = (byte[]) file.buffers.get(currentBufferIndex);
+      currentBuffer = (byte[]) file.getBuffer(currentBufferIndex);
       bufferPosition = 0;
       bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
       long buflen = length - bufferStart;
diff --git a/src/java/org/apache/lucene/store/RAMOutputStream.java b/src/java/org/apache/lucene/store/RAMOutputStream.java
index 7dec81aefc0..b0861807ea2 100644
--- a/src/java/org/apache/lucene/store/RAMOutputStream.java
+++ b/src/java/org/apache/lucene/store/RAMOutputStream.java
@@ -63,7 +63,7 @@ public class RAMOutputStream extends IndexOutput {
       if (nextPos > end) {                        // at the last buffer
         length = (int)(end - pos);
       }
-      out.writeBytes((byte[])file.buffers.get(buffer++), length);
+      out.writeBytes((byte[])file.getBuffer(buffer++), length);
       pos = nextPos;
     }
   }
@@ -124,10 +124,10 @@ public class RAMOutputStream extends IndexOutput {
   }
 
   private final void switchCurrentBuffer() throws IOException {
-    if (currentBufferIndex == file.buffers.size()) {
+    if (currentBufferIndex == file.numBuffers()) {
       currentBuffer = file.addBuffer(BUFFER_SIZE);
     } else {
-      currentBuffer = (byte[]) file.buffers.get(currentBufferIndex);
+      currentBuffer = (byte[]) file.getBuffer(currentBufferIndex);
     }
     bufferPosition = 0;
     bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;