diff --git a/salt/modules/schedule.py b/salt/modules/schedule.py
index a0d813cada7f..fdb8bafa2dc8 100644
--- a/salt/modules/schedule.py
+++ b/salt/modules/schedule.py
@@ -515,6 +515,10 @@ def modify(name, **kwargs):
         return ret
 
     _current = current_schedule[name]
+
+    if 'function' not in kwargs:
+        kwargs['function'] = _current.get('function')
+
     if '_seconds' in _current:
         _current['seconds'] = _current['_seconds']
         del _current['_seconds']
diff --git a/tests/unit/modules/test_schedule.py b/tests/unit/modules/test_schedule.py
index 884f25766892..2ac3a2d5c305 100644
--- a/tests/unit/modules/test_schedule.py
+++ b/tests/unit/modules/test_schedule.py
@@ -20,6 +20,7 @@
 import salt.modules.schedule as schedule
 from salt.utils.event import SaltEvent
 
+
 JOB1 = {'function': 'test.ping', 'maxrunning': 1, 'name': 'job1',
         'jid_include': True, 'enabled': True}
 
@@ -360,3 +361,79 @@ def test_copy(self):
                                                      {'comment': comm3,
                                                       'minions': ['minion1'],
                                                       'result': True})
+
+    # 'modify' function tests: 1
+
+    def test_modify(self):
+        '''
+        Test if modifying job to the schedule.
+        '''
+        job1 = {'function': 'salt', 'seconds': 3600}
+
+        comm1 = 'Modified job: job1 in schedule.'
+        diff1 = ('--- \n+++ \n@@ -1,3 +1,6 @@\n '
+                 'enabled:True\n function:salt\n'
+                 '-seconds:3600\n+jid_include:True\n'
+                 '+maxrunning:1\n+name:job1\n'
+                 '+seconds:60\n')
+
+        diff4 = ('--- \n+++ \n@@ -1,3 +1,5 @@\n '
+                 'enabled:True\n-function:salt\n'
+                 '-seconds:3600\n+function:test.version\n'
+                 '+jid_include:True\n+maxrunning:1\n'
+                 '+name:job1\n')
+
+        expected1 = {'comment': comm1,
+                     'changes': {'diff': diff1},
+                     'result': True}
+
+        comm2 = 'Error: Unable to use "seconds", "minutes", "hours", ' \
+                'or "days" with "when" option.'
+        expected2 = {'comment': comm2,
+                     'changes': {},
+                     'result': False}
+
+        comm3 = 'Unable to use "when" and "cron" options together.  Ignoring.'
+        expected3 = {'comment': comm3,
+                     'changes': {},
+                     'result': False}
+
+        comm4 = 'Job: job1 would be modified in schedule.'
+        expected4 = {'comment': comm4,
+                     'changes': {'diff': diff4},
+                     'result': True}
+
+        comm5 = 'Job job2 does not exist in schedule.'
+        expected5 = {'comment': comm5,
+                     'changes': {},
+                     'result': False}
+
+        with patch.dict(schedule.__opts__, {'schedule': {'job1': job1}, 'sock_dir': self.sock_dir}):
+            mock = MagicMock(return_value=True)
+            with patch.dict(schedule.__salt__, {'event.fire': mock}):
+                _ret_value = {'complete': True, 'schedule': {'job1': job1}}
+                with patch.object(SaltEvent, 'get_event', return_value=_ret_value):
+                    ret = schedule.modify('job1', seconds='60')
+                    self.assertDictEqual(ret, expected1)
+
+                _ret_value = {'complete': True, 'schedule': {'job1': job1}}
+                with patch.object(SaltEvent, 'get_event', return_value=_ret_value):
+                    ret = schedule.modify('job1', function='test.ping',
+                                          seconds=3600, when='2400')
+                    self.assertDictEqual(ret, expected2)
+
+                _ret_value = {'complete': True, 'schedule': {'job1': job1}}
+                with patch.object(SaltEvent, 'get_event', return_value=_ret_value):
+                    ret = schedule.modify('job1', function='test.ping',
+                                          when='2400', cron='2')
+                    self.assertDictEqual(ret, expected3)
+
+                _ret_value = {'complete': True, 'schedule': {'job1': job1}}
+                with patch.object(SaltEvent, 'get_event', return_value=_ret_value):
+                    ret = schedule.modify('job1', function='test.version', test=True)
+                    self.assertDictEqual(ret, expected4)
+
+                _ret_value = {'complete': True, 'schedule': {}}
+                with patch.object(SaltEvent, 'get_event', return_value=_ret_value):
+                    ret = schedule.modify('job2', function='test.version', test=True)
+                    self.assertDictEqual(ret, expected5)