diff --git a/jstests/sharding/key_string.js b/jstests/sharding/key_string.js
index 48948b7ddbd95..bbc5dfb49ec1e 100644
--- a/jstests/sharding/key_string.js
+++ b/jstests/sharding/key_string.js
@@ -39,6 +39,11 @@ assert.eq( 6 , db.foo.find().sort( { name : 1 } ).count() , "total count with co
 assert.eq( "allan,bob,eliot,joe,mark,sara" ,  db.foo.find().sort( { name : 1 } ).toArray().map( function(z){ return z.name; } ) , "sort 1" );
 assert.eq( "sara,mark,joe,eliot,bob,allan" ,  db.foo.find().sort( { name : -1 } ).toArray().map( function(z){ return z.name; } ) , "sort 2" );
 
+// make sure we can't foce a split on an extreme key
+// [allan->joe) 
+assert.throws( function(){ s.adminCommand( { split : "test.foo" , middle : { name : "allan" } } ) } );
+assert.throws( function(){ s.adminCommand( { split : "test.foo" , middle : { name : "joe" } } ) } );
+
 s.stop();
 
 
diff --git a/s/commands_admin.cpp b/s/commands_admin.cpp
index a10f2bebd9d44..6a1da3b83aa71 100644
--- a/s/commands_admin.cpp
+++ b/s/commands_admin.cpp
@@ -479,19 +479,25 @@ namespace mongo {
                 }
                 
                 ChunkManagerPtr info = config->getChunkManager( ns );
-                ChunkPtr old = info->findChunk( find );
-
+                ChunkPtr chunk = info->findChunk( find );
                 BSONObj middle = cmdObj.getObjectField( "middle" );
 
-                assert( old.get() );
-                log() << "splitting: " << ns << "  shard: " << old << endl;
+                assert( chunk.get() );
+                log() << "splitting: " << ns << "  shard: " << chunk << endl;
 
                 if ( middle.isEmpty() )
-                    old->simpleSplit( true /* force a split even if not enough data */ );
+                    chunk->simpleSplit( true /* force a split even if not enough data */ );
+
                 else {
+                    // sanity check if the key provided is a valid split point
+                    if ( ( middle == chunk->getMin() ) || ( middle == chunk->getMax() ) ) {
+                        errmsg = "cannot split on initial or final chunk's key";
+                        return false;
+                    }
+
                     vector<BSONObj> splitPoints;
                     splitPoints.push_back( middle );
-                    old->multiSplit( splitPoints );
+                    chunk->multiSplit( splitPoints );
                 }
 
                 return true;