diff --git a/src/java/org/apache/poi/hssf/model/Sheet.java b/src/java/org/apache/poi/hssf/model/Sheet.java
index 1dbafd7bc..1c87da87b 100644
--- a/src/java/org/apache/poi/hssf/model/Sheet.java
+++ b/src/java/org/apache/poi/hssf/model/Sheet.java
@@ -476,6 +476,10 @@ public class Sheet implements Model
             records.remove(removePos);
 				mergedRecords.remove(pos);
             mergedLocs.remove(pos);
+            
+            //if we're not tracking merged records, kill the pointer to reset the state
+            if (mergedRecords.size() == 0) merged = null;
+            
         }
     }
 
diff --git a/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFSheet.java b/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFSheet.java
index 66d475edc..f021c5439 100644
--- a/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFSheet.java
+++ b/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFSheet.java
@@ -276,6 +276,25 @@ public class TestHSSFSheet
     	assertEquals("Left over region should be starting at row 1", 1, region.getRowFrom());
     	
     	sheet.removeMergedRegion(0);
+    	
+		assertEquals("there should be no merged regions left!", 0, sheet.getNumMergedRegions());
+		
+		//an, add, remove, get(0) would null pointer
+		sheet.addMergedRegion(region);
+		assertEquals("there should now be one merged region!", 1, sheet.getNumMergedRegions());
+		sheet.removeMergedRegion(0);
+		assertEquals("there should now be zero merged regions!", 0, sheet.getNumMergedRegions());
+		//add it again!
+		region.setRowTo(4);
+    	
+		sheet.addMergedRegion(region);
+		assertEquals("there should now be one merged region!", 1, sheet.getNumMergedRegions());
+		
+		//should exist now!
+		assertTrue("there isn't more than one merged region in there", 1 <= sheet.getNumMergedRegions());
+		region = sheet.getMergedRegionAt(0);
+		assertEquals("the merged row to doesnt match the one we put in ", 4, region.getRowTo());
+    	
     }
 
 	public static void main(java.lang.String[] args) {