diff --git a/src/commands/CmdTag.cpp b/src/commands/CmdTag.cpp
index 89e48fc7..623b92c2 100644
--- a/src/commands/CmdTag.cpp
+++ b/src/commands/CmdTag.cpp
@@ -41,6 +41,11 @@ int CmdTag (
   std::set <int> ids = cli.getIds ();
   std::vector<std::string> tags = cli.getTags ();
 
+  if (tags.empty ())
+  {
+    throw std::string ("At least one tag must be specified. See 'timew help tag'.");
+  }
+
   // Load the data.
   // Note: There is no filter.
   Interval filter;
diff --git a/test/tag.t b/test/tag.t
index 814b8866..cc8a8c13 100755
--- a/test/tag.t
+++ b/test/tag.t
@@ -56,6 +56,12 @@ class TestTag(TestCase):
         code, out, err = self.t.runError("tag foo")
         self.assertIn("At least one ID must be specified.", err)
 
+    def test_should_fail_on_no_tags(self):
+        """No tags is an error"""
+        self.t("track yesterday for 1hour")
+        code, out, err = self.t.runError("tag @1")
+        self.assertIn("At least one tag must be specified.", err)
+
     def test_add_tag_to_closed_interval(self):
         """Add a tag to an closed interval"""
         self.t("track yesterday for 1hour")