diff --git a/Cargo.toml b/Cargo.toml
index 80ee7d5..4c74c3c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 
 name = "yup-oauth2"
-version = "5.0.1"
+version = "5.0.2"
 authors = ["Sebastian Thiel <byronimo@gmail.com>", "Lewin Bormann <lbo@spheniscida.de>"]
 repository = "https://github.com/dermesser/yup-oauth2"
 description = "An oauth2 implementation, providing the 'device', 'service account' and 'installed' authorization flows"
diff --git a/src/installed.rs b/src/installed.rs
index 41507bb..402ff61 100644
--- a/src/installed.rs
+++ b/src/installed.rs
@@ -36,8 +36,18 @@ where
     let scopes_string = crate::helper::join(scopes, " ");
 
     url.push_str(auth_uri);
+
+    if !url.contains('?') {
+        url.push('?');
+    } else {
+        match url.chars().last() {
+            Some('?') | None => {}
+            Some(_) => url.push('&'),
+        }
+    }
+
     vec![
-        format!("?scope={}", scopes_string),
+        format!("scope={}", scopes_string),
         "&access_type=offline".to_string(),
         format!("&redirect_uri={}", redirect_uri.unwrap_or(OOB_REDIRECT_URI)),
         "&response_type=code".to_string(),
@@ -371,6 +381,23 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_request_url_builder_appends_queries() {
+        assert_eq!(
+            "https://accounts.google.\
+             com/o/oauth2/auth?unknown=testing&scope=email%20profile&access_type=offline&redirect_uri=urn:ietf:wg:oauth:2.0:\
+             oob&response_type=code&client_id=812741506391-h38jh0j4fv0ce1krdkiq0hfvt6n5amr\
+             f.apps.googleusercontent.com",
+            build_authentication_request_url(
+                "https://accounts.google.com/o/oauth2/auth?unknown=testing",
+                "812741506391-h38jh0j4fv0ce1krdkiq0hfvt6n5am\
+                 rf.apps.googleusercontent.com",
+                &["email", "profile"],
+                None
+            )
+        );
+    }
+
     #[tokio::test]
     async fn test_server_random_local_port() {
         let addr1 = InstalledFlowServer::run().unwrap().local_addr();