diff --git a/ext/on-modify.timewarrior b/ext/on-modify.timewarrior
index 6ca0b08d..0e7500c9 100644
--- a/ext/on-modify.timewarrior
+++ b/ext/on-modify.timewarrior
@@ -42,7 +42,7 @@ old = json.loads(sys.stdin.readline())
 new = json.loads(sys.stdin.readline())
 print(json.dumps(new))
 
-def get_timew_name_from_json(json_obj):
+def extract_timew_tags_from(json_obj):
     # Extract attributes for use as tags.
     tags = [json_obj['description']]
 
@@ -52,7 +52,7 @@ def get_timew_name_from_json(json_obj):
     if 'tags' in json_obj:
         tags.extend(json_obj['tags'])
 
-    return ' '.join(['"%s"' % tag for tag in tags]).encode('utf-8').strip()
+    return ' '.join(['"{0}"'.format(tag) for tag in tags]).encode('utf-8').strip()
 
 start_or_stop = ''
 
@@ -65,19 +65,15 @@ elif 'start' not in new and 'start' in old:
     start_or_stop = 'stop'
 
 if start_or_stop:
-    combined = get_timew_name_from_json(new)
+    combined = extract_timew_tags_from(new)
 
-    command = 'timew {0} {1} :yes'.format(start_or_stop, combined)
-    subprocess.call(shlex.split(command))
+    subprocess.call(shlex.split('timew {0} {1} :yes'.format(start_or_stop, combined)))
 
 # Modifications to task other than start/stop
 elif 'start' in new and 'start' in old:
-    old_combined = get_timew_name_from_json(old)
-    new_combined = get_timew_name_from_json(new)
+    old_combined = extract_timew_tags_from(old)
+    new_combined = extract_timew_tags_from(new)
 
     if old_combined != new_combined:
-        command = 'timew stop {0} :yes'.format(old_combined)
-        subprocess.call(shlex.split(command))
-
-        command = 'timew start {0} :yes'.format(new_combined)
-        subprocess.call(shlex.split(command))
+        subprocess.call(shlex.split('timew untag @1 {0} :yes'.format(old_combined)))
+        subprocess.call(shlex.split('timew tag @1 {0} :yes'.format(new_combined)))
diff --git a/test/test_on-modify.timewarrior.t.py b/test/test_on-modify.timewarrior.t.py
index 93e5d630..4eda9a18 100755
--- a/test/test_on-modify.timewarrior.t.py
+++ b/test/test_on-modify.timewarrior.t.py
@@ -120,10 +120,8 @@ class TestOnModifyHookScript(TestCase):
 """)
 
         self.assertRegexpMatches(out, """\
-Tracking foo
-  Started \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}
-  Current               (\d{2}:|   )\d{2}
-  Total                ?\d{1,2}:\d{2}:\d{2}
+Removed dummy from @1
+Added foo to @1
 \{"status": "pending", "uuid": "3422d76c-c087-4ecd-9c62-1246b078e534", "modified": "20180317T092629Z", "start": "20180317T092629Z", "entry": "20180317T092629Z", "description": "foo"\}
 """)
         self.assertEqual('', err)
@@ -138,14 +136,8 @@ Tracking foo
 """)
 
         self.assertRegexpMatches(out, """\
-Recorded dummy tag1 tag2
-  Started \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}
-  Ended                 (\d{2}:|   )\d{2}
-  Total               ?\d{1,2}:\d{2}:\d{2}
-Tracking dummy tag3 tag4
-  Started \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}
-  Current               (\d{2}:|   )\d{2}
-  Total                ?\d{1,2}:\d{2}:\d{2}
+Removed dummy tag1 tag2 from @1
+Added dummy tag3 tag4 to @1
 \{"status": "pending", "uuid": "3422d76c-c087-4ecd-9c62-1246b078e534", "tags": \["tag3", "tag4"\], "modified": "20180317T092629Z", "start": "20180317T092629Z", "entry": "20180317T092629Z", "description": "dummy"\}
 """)
         self.assertEqual('', err)
@@ -160,14 +152,8 @@ Tracking dummy tag3 tag4
 """)
 
         self.assertRegexpMatches(out, """\
-Recorded dummy proj1
-  Started \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}
-  Ended                 (\d{2}:|   )\d{2}
-  Total               ?\d{1,2}:\d{2}:\d{2}
-Tracking dummy proj2
-  Started \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}
-  Current               (\d{2}:|   )\d{2}
-  Total                ?\d{1,2}:\d{2}:\d{2}
+Removed dummy proj1 from @1
+Added dummy proj2 to @1
 \{"status": "pending", "uuid": "3422d76c-c087-4ecd-9c62-1246b078e534", "modified": "20180317T092629Z", "project": "proj2", "start": "20180317T092629Z", "entry": "20180317T092629Z", "description": "dummy"\}
 """)
         self.assertEqual('', err)