3 files changed, 17 insertions, 0 deletions
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index 935454636..ec871d927 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -2073,6 +2073,12 @@ itest!(unstable_enabled_js {
   output: "unstable_enabled_js.out",
 });
 
+itest!(unstable_disabled_ts2551 {
+  args: "run --reload unstable_ts2551.ts",
+  exit_code: 1,
+  output: "unstable_disabled_ts2551.out",
+});
+
 itest!(_053_import_compression {
   args: "run --quiet --reload --allow-net 053_import_compression/main.ts",
   output: "053_import_compression.out",
diff --git a/cli/tests/unstable_disabled_ts2551.out b/cli/tests/unstable_disabled_ts2551.out
new file mode 100644
index 000000000..bf8e6872b
--- /dev/null
+++ b/cli/tests/unstable_disabled_ts2551.out
@@ -0,0 +1,10 @@
+[WILDCARD]
+error: TS2551 [ERROR]: Property 'ppid' does not exist on type 'typeof Deno'. 'Deno.ppid' is an unstable API. Did you forget to run with the '--unstable' flag, or did you mean 'pid'?
+console.log(Deno.ppid);
+                 ~~~~
+    at [WILDCARD]cli/tests/unstable_ts2551.ts:1:18
+
+    'pid' is declared here.
+      export const pid: number;
+                   ~~~
+        at asset:///lib.deno.ns.d.ts:[WILDCARD]
diff --git a/cli/tests/unstable_ts2551.ts b/cli/tests/unstable_ts2551.ts
new file mode 100644
index 000000000..c9016c56c
--- /dev/null
+++ b/cli/tests/unstable_ts2551.ts
@@ -0,0 +1 @@
+console.log(Deno.ppid);