Index: lucene/suggest/src/java/org/apache/lucene/search/suggest/fst/Sort.java
===================================================================
--- lucene/suggest/src/java/org/apache/lucene/search/suggest/fst/Sort.java	(revision 1341810)
+++ lucene/suggest/src/java/org/apache/lucene/search/suggest/fst/Sort.java	(working copy)
@@ -37,18 +37,18 @@
  * @lucene.internal
  */
 public final class Sort {
-  public final static int MB = 1024 * 1024;
-  public final static int GB = MB * 1024;
+  public final static long MB = 1024 * 1024;
+  public final static long GB = MB * 1024;
   
   /**
    * Minimum recommended buffer size for sorting.
    */
-  public final static int MIN_BUFFER_SIZE_MB = 32;
+  public final static long MIN_BUFFER_SIZE_MB = 32;
 
   /**
    * Absolute minimum required buffer size for sorting.
    */
-  public static final int ABSOLUTE_MIN_SORT_BUFFER_SIZE = MB / 2;
+  public static final long ABSOLUTE_MIN_SORT_BUFFER_SIZE = MB / 2;
   private static final String MIN_BUFFER_SIZE_MSG = "At least 0.5MB RAM buffer is needed";
 
   /**
@@ -70,11 +70,15 @@
         throw new IllegalArgumentException("Buffer too large for Java ("
             + (Integer.MAX_VALUE / MB) + "mb max): " + bytes);
       }
+      
+      if (bytes < ABSOLUTE_MIN_SORT_BUFFER_SIZE) {
+        throw new IllegalArgumentException(MIN_BUFFER_SIZE_MSG + ": " + bytes);
+      }
   
       this.bytes = (int) bytes;
     }
   
-    public static BufferSize megabytes(int mb) {
+    public static BufferSize megabytes(long mb) {
       return new BufferSize(mb * MB);
     }
   
@@ -105,7 +109,7 @@
           sortBufferByteSize = Math.max(ABSOLUTE_MIN_SORT_BUFFER_SIZE, sortBufferByteSize);
         }
       }
-      return new BufferSize(Math.min(Integer.MAX_VALUE, sortBufferByteSize));
+      return new BufferSize(Math.min((long)Integer.MAX_VALUE, sortBufferByteSize));
     }
   }
   
Index: lucene/suggest/src/test/org/apache/lucene/search/suggest/fst/TestSort.java
===================================================================
--- lucene/suggest/src/test/org/apache/lucene/search/suggest/fst/TestSort.java	(revision 1341810)
+++ lucene/suggest/src/test/org/apache/lucene/search/suggest/fst/TestSort.java	(working copy)
@@ -63,7 +63,7 @@
   public void testIntermediateMerges() throws Exception {
     // Sort 20 mb worth of data with 1mb buffer, binary merging.
     SortInfo info = checkSort(new Sort(Sort.DEFAULT_COMPARATOR, BufferSize.megabytes(1), Sort.defaultTempDir(), 2), 
-        generateRandom(Sort.MB * 20));
+        generateRandom((int)Sort.MB * 20));
     assertTrue(info.mergeRounds > 10);
   }
 
@@ -71,7 +71,7 @@
   public void testSmallRandom() throws Exception {
     // Sort 20 mb worth of data with 1mb buffer.
     SortInfo sortInfo = checkSort(new Sort(Sort.DEFAULT_COMPARATOR, BufferSize.megabytes(1), Sort.defaultTempDir(), Sort.MAX_TEMPFILES), 
-        generateRandom(Sort.MB * 20));
+        generateRandom((int)Sort.MB * 20));
     assertEquals(1, sortInfo.mergeRounds);
   }
 
@@ -79,7 +79,7 @@
   public void testLargerRandom() throws Exception {
     // Sort 100MB worth of data with 15mb buffer.
     checkSort(new Sort(Sort.DEFAULT_COMPARATOR, BufferSize.megabytes(16), Sort.defaultTempDir(), Sort.MAX_TEMPFILES), 
-        generateRandom(Sort.MB * 100));
+        generateRandom((int)Sort.MB * 100));
   }
 
   private byte[][] generateRandom(int howMuchData) {
@@ -152,4 +152,31 @@
     w.close();
     return file;
   }
+  
+  public void testRamBuffer() {
+    int numIters = atLeast(10000);
+    for (int i = 0; i < numIters; i++) {
+      BufferSize.megabytes(1+random().nextInt(2047));
+    }
+    BufferSize.megabytes(2047);
+    BufferSize.megabytes(1);
+    
+    try {
+      BufferSize.megabytes(2048);
+      fail("max mb is 2047");
+    } catch (IllegalArgumentException e) {
+    }
+    
+    try {
+      BufferSize.megabytes(0);
+      fail("min mb is 0.5");
+    } catch (IllegalArgumentException e) {
+    }
+    
+    try {
+      BufferSize.megabytes(-1);
+      fail("min mb is 0.5");
+    } catch (IllegalArgumentException e) {
+    }
+  }
 }