diff --git a/src/documentation/content/xdocs/status.xml b/src/documentation/content/xdocs/status.xml
index 1d561f8097..d9eb624850 100644
--- a/src/documentation/content/xdocs/status.xml
+++ b/src/documentation/content/xdocs/status.xml
@@ -34,6 +34,7 @@
 
     <changes>
         <release version="3.7-SNAPSHOT" date="2010-??-??">
+           <action dev="POI-DEVELOPERS" type="fix">49139 - Properly support 4k big block size in POIFS</action>
            <action dev="POI-DEVELOPERS" type="fix">48936 - Avoid writing malformed CDATA blocks in sharedStrings.xml</action>
            <action dev="POI-DEVELOPERS" type="add">49026 - Added implementation for TEXT()  </action>
            <action dev="POI-DEVELOPERS" type="add">49025 - Added implementation for TRUNC()  </action>
diff --git a/src/java/org/apache/poi/poifs/common/POIFSBigBlockSize.java b/src/java/org/apache/poi/poifs/common/POIFSBigBlockSize.java
index 19b345d716..1e8b1b113a 100644
--- a/src/java/org/apache/poi/poifs/common/POIFSBigBlockSize.java
+++ b/src/java/org/apache/poi/poifs/common/POIFSBigBlockSize.java
@@ -38,6 +38,12 @@ public final class POIFSBigBlockSize
       return bigBlockSize;
    }
    
+   /**
+    * Returns the value that gets written into the 
+    *  header.
+    * Is the power of two that corresponds to the
+    *  size of the block, eg 512 => 9
+    */
    public short getHeaderValue() {
       return headerValue;
    }
diff --git a/src/java/org/apache/poi/poifs/dev/POIFSHeaderDumper.java b/src/java/org/apache/poi/poifs/dev/POIFSHeaderDumper.java
index 1967daec43..75f69caebf 100644
--- a/src/java/org/apache/poi/poifs/dev/POIFSHeaderDumper.java
+++ b/src/java/org/apache/poi/poifs/dev/POIFSHeaderDumper.java
@@ -149,6 +149,8 @@ public class POIFSHeaderDumper {
             bnS = "DI Fat Block";
          } else if(bn == POIFSConstants.FAT_SECTOR_BLOCK) {
             bnS = "Normal Fat Block";
+         } else if(bn == POIFSConstants.UNUSED_BLOCK) {
+            bnS = "Block Not Used (Free)";
          }
          
          System.out.println("  Block  # " + i + " -> " + bnS);
diff --git a/src/java/org/apache/poi/poifs/storage/DocumentBlock.java b/src/java/org/apache/poi/poifs/storage/DocumentBlock.java
index 3f84fa6e61..a7c5686257 100644
--- a/src/java/org/apache/poi/poifs/storage/DocumentBlock.java
+++ b/src/java/org/apache/poi/poifs/storage/DocumentBlock.java
@@ -32,10 +32,6 @@ import org.apache.poi.util.IOUtils;
  * @author Marc Johnson (mjohnson at apache dot org)
  */
 public final class DocumentBlock extends BigBlock {
-    private static final int BLOCK_SHIFT = 9;
-    private static final int BLOCK_SIZE = 1 << BLOCK_SHIFT;
-    private static final int BLOCK_MASK = BLOCK_SIZE-1;
-
     private static final byte _default_value = ( byte ) 0xFF;
     private byte[]            _data;
     private int               _bytes_read;
@@ -165,6 +161,17 @@ public final class DocumentBlock extends BigBlock {
     }
 
     public static DataInputBlock getDataInputBlock(DocumentBlock[] blocks, int offset) {
+        if(blocks == null || blocks.length == 0) {
+           return null;
+        }
+        
+        // Key things about the size of the block
+        POIFSBigBlockSize bigBlockSize = blocks[0].bigBlockSize;
+        int BLOCK_SHIFT = bigBlockSize.getHeaderValue();
+        int BLOCK_SIZE = bigBlockSize.getBigBlockSize();
+        int BLOCK_MASK = BLOCK_SIZE - 1;
+
+        // Now do the offset lookup
         int firstBlockIndex = offset >> BLOCK_SHIFT;
         int firstBlockOffset= offset & BLOCK_MASK;
         return new DataInputBlock(blocks[firstBlockIndex]._data, firstBlockOffset);
diff --git a/src/testcases/org/apache/poi/poifs/filesystem/TestPOIFSFileSystem.java b/src/testcases/org/apache/poi/poifs/filesystem/TestPOIFSFileSystem.java
index 1b370124f6..5ebc168941 100644
--- a/src/testcases/org/apache/poi/poifs/filesystem/TestPOIFSFileSystem.java
+++ b/src/testcases/org/apache/poi/poifs/filesystem/TestPOIFSFileSystem.java
@@ -177,9 +177,8 @@ public final class TestPOIFSFileSystem extends TestCase {
 	/**
 	 * Most OLE2 files use 512byte blocks. However, a small number
 	 *  use 4k blocks. Check that we can open these.
-	 * DISABLED until we fix the bug with DocumentBlocks on 4k sizes
 	 */
-	public void DISABLEDtest4KBlocks() throws Exception {
+	public void test4KBlocks() throws Exception {
       POIDataSamples _samples = POIDataSamples.getPOIFSInstance();
 	   InputStream inp = _samples.openResourceAsStream("BlockSize4096.zvi");
 	   
@@ -219,7 +218,8 @@ public final class TestPOIFSFileSystem extends TestCase {
 	      if(entry instanceof DirectoryEntry) {
 	         checkAllDirectoryContents((DirectoryEntry)entry);
 	      } else {
-	         DocumentInputStream dis = new DocumentInputStream((DocumentNode) entry);
+	         DocumentNode doc = (DocumentNode) entry;
+	         DocumentInputStream dis = new DocumentInputStream(doc);
 	         int numBytes = dis.available();
 	         byte[] data = new byte [numBytes];
             dis.read(data);