diff --git a/dj_database_url.py b/dj_database_url.py
index 39f7405..ac194a4 100644
--- a/dj_database_url.py
+++ b/dj_database_url.py
@@ -115,7 +115,13 @@ def parse(
         hostname = urlparse.unquote(hostname)
 
     # Lookup specified engine.
-    engine = SCHEMES[url.scheme] if engine is None else engine
+    if engine is None:
+        engine = SCHEMES.get(url.scheme)
+        if engine is None:
+            raise ValueError(
+                "No support for '%s'. We support: %s"
+                % (url.scheme, ", ".join(sorted(SCHEMES.keys())))
+            )
 
     port = (
         str(url.port)
diff --git a/test_dj_database_url.py b/test_dj_database_url.py
index a10625a..0ed8b02 100644
--- a/test_dj_database_url.py
+++ b/test_dj_database_url.py
@@ -541,6 +541,10 @@ class DatabaseTestSuite(unittest.TestCase):
         assert url["CONN_MAX_AGE"] == 600
         assert url["CONN_HEALTH_CHECKS"] is True
 
+    def test_bad_url_parsing(self):
+        with self.assertRaisesRegex(ValueError, "No support for 'foo'. We support: "):
+            dj_database_url.parse("foo://bar")
+
 
 if __name__ == "__main__":
     unittest.main()