diff --git a/src/main/java/com/tencent/angel/ml/math2/matrix/MapMatrix.java b/src/main/java/com/tencent/angel/ml/math2/matrix/MapMatrix.java
index 4d27f1d..97860e8 100755
--- a/src/main/java/com/tencent/angel/ml/math2/matrix/MapMatrix.java
+++ b/src/main/java/com/tencent/angel/ml/math2/matrix/MapMatrix.java
@@ -37,7 +37,7 @@ public MapMatrix(HashMap<Long, Vec> mapMatrix) {
   }
 
   public Vector getRow(int idx) {
-    return mapMatrix.get(idx);
+    return mapMatrix.get((long) idx);
   }
 
   public Vector getRow(long idx) {
@@ -47,7 +47,7 @@ public Vector getRow(long idx) {
   public HashMap<Long, Vec> getRows(int[] idx) {
     HashMap<Long, Vec> matrix = new HashMap();
     for (int id : idx) {
-      matrix.put((long) id, mapMatrix.get(id));
+      matrix.put((long) id, mapMatrix.get((long) id));
     }
     return matrix;
   }