diff --git a/emark/message.py b/emark/message.py
index 868f612..b08f7a6 100644
--- a/emark/message.py
+++ b/emark/message.py
@@ -131,10 +131,10 @@ def inject_utm_params(self, md, **utm):
         for url in INLINE_LINK_RE.findall(md):
             try:
                 url_parts = parse.urlparse(url)
-                if url_parts.scheme and url_parts.scheme not in [
+                if url_parts.scheme not in [
                     "http",
                     "https",
-                    "localhost",
+                    "",
                 ]:
                     continue
             except ValueError:
@@ -143,10 +143,10 @@ def inject_utm_params(self, md, **utm):
         for url in INLINE_HTML_LINK_RE.findall(md):
             try:
                 url_parts = parse.urlparse(url)
-                if url_parts.scheme and url_parts.scheme not in [
+                if url_parts.scheme not in [
                     "http",
                     "https",
-                    "localhost",
+                    "",
                 ]:
                     continue
             except ValueError:
diff --git a/tests/test_message.py b/tests/test_message.py
index 70eae0d..6853250 100644
--- a/tests/test_message.py
+++ b/tests/test_message.py
@@ -281,7 +281,7 @@ def test_inject_utm_params(self):
             in email_message.body
         )
         assert (
-            "localhost:8000 <localhost:8000?utm_source=website&utm_medium=email&utm_campaign=MARKDOWN_EMAIL_TEST_WITH_SUBJECT>"
+            "localhost:8000 <http://localhost:8000?utm_source=website&utm_medium=email&utm_campaign=MARKDOWN_EMAIL_TEST_WITH_SUBJECT>"
             in email_message.body
         )
         assert "555-2368 <tel:5552368>" in email_message.body
diff --git a/tests/testapp/templates/template.md b/tests/testapp/templates/template.md
index ffc4c61..c597367 100644
--- a/tests/testapp/templates/template.md
+++ b/tests/testapp/templates/template.md
@@ -13,7 +13,7 @@ Vanilla lollipop biscuit cake marzipan jelly.
 [A link with parameter](https://www.example.com/?foo=bar)
 [A link without a scheme](www.example.com)
 [A link without www](example.com)
-[localhost:8000](localhost:8000)
+[localhost:8000](http://localhost:8000)
 [555-2368](tel:5552368)
 
 <a href="https://www.example.com/html">An HTML Link</a>