diff --git a/swh/web/common/archive.py b/swh/web/common/archive.py
--- a/swh/web/common/archive.py
+++ b/swh/web/common/archive.py
@@ -248,6 +248,9 @@
         # slash while the url in storage have it (e.g. Debian source package)
         else:
             origin_urls.append(f"{origin['url']}/")
+        # handle case where the "://" character sequence was mangled into ":/"
+        if ":/" in origin["url"] and "://" not in origin["url"]:
+            origin_urls.append(origin["url"].replace(":/", "://"))
     origins = [o for o in storage.origin_get(origin_urls) if o is not None]
     if not origins:
         msg = "Origin with url %s not found!" % origin["url"]
diff --git a/swh/web/tests/common/test_archive.py b/swh/web/tests/common/test_archive.py
--- a/swh/web/tests/common/test_archive.py
+++ b/swh/web/tests/common/test_archive.py
@@ -975,6 +975,14 @@
     assert origin_info["url"] == deb_origin.url
 
 
+def test_lookup_origin_single_slash_after_protocol(archive_data):
+    url = "http://snapshot.debian.org/package/r-base/"
+    deb_origin = Origin(url=url)
+    archive_data.origin_add([deb_origin])
+    origin_info = archive.lookup_origin({"url": url.replace("://", ":/")})
+    assert origin_info["url"] == deb_origin.url
+
+
 @given(snapshot())
 def test_lookup_snapshot_branch_name_from_tip_revision(archive_data, snapshot_id):
     snapshot = archive_data.snapshot_get(snapshot_id)