diff --git a/salt/utils/master.py b/salt/utils/master.py
index ca0f2de7c5..946f36a306 100755
--- a/salt/utils/master.py
+++ b/salt/utils/master.py
@@ -108,7 +108,7 @@ class MasterPillarUtil(object):
                     continue
                 path = os.path.join(mdir, minion_id, 'mine.p')
                 if os.path.isfile(path):
-                    with salt.utils.fopen(path) as fp_:
+                    with salt.utils.fopen(path, 'rb') as fp_:
                         mdata = self.serial.loads(fp_.read())
                         if isinstance(mdata, dict):
                             mine_data[minion_id] = mdata
@@ -132,7 +132,7 @@ class MasterPillarUtil(object):
                     continue
                 path = os.path.join(mdir, minion_id, 'data.p')
                 if os.path.isfile(path):
-                    with salt.utils.fopen(path) as fp_:
+                    with salt.utils.fopen(path, 'rb') as fp_:
                         mdata = self.serial.loads(fp_.read())
                         if mdata.get('grains', False):
                             grains[minion_id] = mdata['grains']
@@ -363,21 +363,21 @@ class MasterPillarUtil(object):
                     # Not saving pillar or grains, so just delete the cache file
                     os.remove(os.path.join(data_file))
                 elif clear_pillar and minion_grains:
-                    with salt.utils.fopen(data_file, 'w+') as fp_:
+                    with salt.utils.fopen(data_file, 'w+b') as fp_:
                         fp_.write(self.serial.dumps({'grains': minion_grains}))
                 elif clear_grains and minion_pillar:
-                    with salt.utils.fopen(data_file, 'w+') as fp_:
+                    with salt.utils.fopen(data_file, 'w+b') as fp_:
                         fp_.write(self.serial.dumps({'pillar': minion_pillar}))
                 if clear_mine:
                     # Delete the whole mine file
                     os.remove(os.path.join(mine_file))
                 elif clear_mine_func is not None:
                     # Delete a specific function from the mine file
-                    with salt.utils.fopen(mine_file) as fp_:
+                    with salt.utils.fopen(mine_file, 'rb') as fp_:
                         mine_data = self.serial.loads(fp_.read())
                     if isinstance(mine_data, dict):
                         if mine_data.pop(clear_mine_func, False):
-                            with salt.utils.fopen(mine_file, 'w+') as fp_:
+                            with salt.utils.fopen(mine_file, 'w+b') as fp_:
                                 fp_.write(self.serial.dumps(mine_data))
         except (OSError, IOError):
             return True