diff --git a/src/cargo/core/features.rs b/src/cargo/core/features.rs
index 9132f0e08..394ff2a5d 100644
--- a/src/cargo/core/features.rs
+++ b/src/cargo/core/features.rs
@@ -988,29 +988,22 @@ impl CliUnstable {
     pub fn fail_if_stable_opt(&self, flag: &str, issue: u32) -> CargoResult<()> {
         if !self.unstable_options {
             let see = format!(
-                "See https://github.com/rust-lang/cargo/issues/{} for more \
-                 information about the `{}` flag.",
-                issue, flag
+                "See https://github.com/rust-lang/cargo/issues/{issue} for more \
+                 information about the `{flag}` flag."
             );
             // NOTE: a `config` isn't available here, check the channel directly
             let channel = channel();
             if channel == "nightly" || channel == "dev" {
                 bail!(
-                    "the `{}` flag is unstable, pass `-Z unstable-options` to enable it\n\
-                     {}",
-                    flag,
-                    see
+                    "the `{flag}` flag is unstable, pass `-Z unstable-options` to enable it\n\
+                     {see}"
                 );
             } else {
                 bail!(
-                    "the `{}` flag is unstable, and only available on the nightly channel \
-                     of Cargo, but this is the `{}` channel\n\
-                     {}\n\
-                     {}",
-                    flag,
-                    channel,
-                    SEE_CHANNELS,
-                    see
+                    "the `{flag}` flag is unstable, and only available on the nightly channel \
+                     of Cargo, but this is the `{channel}` channel\n\
+                     {SEE_CHANNELS}\n\
+                     {see}"
                 );
             }
         }
diff --git a/src/cargo/ops/registry.rs b/src/cargo/ops/registry.rs
index dea7f703f..d70e86cd1 100644
--- a/src/cargo/ops/registry.rs
+++ b/src/cargo/ops/registry.rs
@@ -807,10 +807,19 @@ pub fn registry_login(
     let new_token;
     if generate_keypair || secret_key_required || key_subject.is_some() {
         if !config.cli_unstable().registry_auth {
-            // todo use fail_if_stable_opt
+            let flag = if generate_keypair {
+                "generate-keypair"
+            } else if secret_key_required {
+                "secret-key"
+            } else if key_subject.is_some() {
+                "key-subject"
+            } else {
+                unreachable!("how did whe get here");
+            };
             bail!(
-                "asymmetric token options are unstable and require the \
-                `-Z registry-auth` option on the nightly channel"
+                "the `{flag}` flag is unstable, pass `-Z registry-auth` to enable it\n\
+                 See https://github.com/rust-lang/cargo/issues/10519 for more \
+                 information about the `{flag}` flag."
             );
         }
         assert!(token.is_none());
diff --git a/tests/testsuite/login.rs b/tests/testsuite/login.rs
index 20ef8d1ba..533309301 100644
--- a/tests/testsuite/login.rs
+++ b/tests/testsuite/login.rs
@@ -1,7 +1,7 @@
 //! Tests for the `cargo login` command.
 
 use cargo_test_support::install::cargo_home;
-use cargo_test_support::registry::RegistryBuilder;
+use cargo_test_support::registry::{self, RegistryBuilder};
 use cargo_test_support::{cargo_process, t};
 use std::fs::{self};
 use std::path::PathBuf;
@@ -154,19 +154,25 @@ fn bad_asymmetric_token_args() {
         .run();
 }
 
-// todo why do theas hang when run as a test?
-// #[cargo_test]
-// fn asymmetric_requires_nightly() {
-//     cargo_process("login --key-subject=foo")
-//         .with_status(101)
-//         .with_stderr_contains("asymmetric token options are unstable and require the `-Z registry-auth` option on the nightly channel")
-//         .run();
-//     cargo_process("login --generate-keypair")
-//         .with_status(101)
-//         .with_stderr_contains("asymmetric token options are unstable and require the `-Z registry-auth` option on the nightly channel")
-//         .run();
-//     cargo_process("login --secret-key")
-//         .with_status(101)
-//         .with_stderr_contains("asymmetric token options are unstable and require the `-Z registry-auth` option on the nightly channel")
-//         .run();
-// }
+#[cargo_test]
+fn asymmetric_requires_nightly() {
+    let registry = registry::init();
+    cargo_process("login --key-subject=foo")          
+        .replace_crates_io(registry.index_url())
+        .with_status(101)
+        .with_stderr_contains("[ERROR] the `key-subject` flag is unstable, pass `-Z registry-auth` to enable it\n\
+            See https://github.com/rust-lang/cargo/issues/10519 for more information about the `key-subject` flag.")
+        .run();
+    cargo_process("login --generate-keypair")
+        .replace_crates_io(registry.index_url())
+        .with_status(101)
+        .with_stderr_contains("[ERROR] the `generate-keypair` flag is unstable, pass `-Z registry-auth` to enable it\n\
+            See https://github.com/rust-lang/cargo/issues/10519 for more information about the `generate-keypair` flag.")
+        .run();
+    cargo_process("login --secret-key")
+        .replace_crates_io(registry.index_url())
+        .with_status(101)
+        .with_stderr_contains("[ERROR] the `secret-key` flag is unstable, pass `-Z registry-auth` to enable it\n\
+            See https://github.com/rust-lang/cargo/issues/10519 for more information about the `secret-key` flag.")
+        .run();
+}