diff --git a/physbo/search/discrete/results.py b/physbo/search/discrete/results.py
index f925830b..75651989 100644
--- a/physbo/search/discrete/results.py
+++ b/physbo/search/discrete/results.py
@@ -183,8 +183,8 @@ def load(self, filename):
 
         """
         data = np.load(filename)
-        M = data["num_runs"]
-        N = data["total_num_search"]
+        M = int(data["num_runs"])
+        N = int(data["total_num_search"])
         self.num_runs = M
         self.total_num_search = N
         self.fx[0:N] = data["fx"]
diff --git a/physbo/search/discrete_multi/results.py b/physbo/search/discrete_multi/results.py
index 96288a86..c711fd42 100644
--- a/physbo/search/discrete_multi/results.py
+++ b/physbo/search/discrete_multi/results.py
@@ -118,8 +118,8 @@ def load(self, filename):
         with open(filename, "rb") as f:
             data = pickle.load(f)
 
-        M = data["num_runs"]
-        N = data["total_num_search"]
+        M = int(data["num_runs"])
+        N = int(data["total_num_search"])
         self.num_runs = M
         self.total_num_search = N
         self.fx[0:N] = data["fx"]