diff --git a/test/libponyc-run/promise-flatten-next-regression-3856/expected-exit-code.txt b/test/libponyc-run/promise-flatten-next-regression-3856/expected-exit-code.txt
new file mode 100644
index 00000000000..c227083464f
--- /dev/null
+++ b/test/libponyc-run/promise-flatten-next-regression-3856/expected-exit-code.txt
@@ -0,0 +1 @@
+0
\ No newline at end of file
diff --git a/test/libponyc-run/promise-flatten-next-regression-3856/main.pony b/test/libponyc-run/promise-flatten-next-regression-3856/main.pony
new file mode 100644
index 00000000000..37059dd73d2
--- /dev/null
+++ b/test/libponyc-run/promise-flatten-next-regression-3856/main.pony
@@ -0,0 +1,24 @@
+use "promises"
+
+actor FlattenNextProbe
+  new create(handler: Handler iso) =>
+    let promise = Promise[String]
+    // We need a call to next to be present with a call to flatten_next to trigger the issue during reachability analysis
+    promise.next[Any tag](recover this~behaviour() end)
+    (consume handler)(recover String end, promise)
+
+  be behaviour(value: String) =>
+    None
+
+
+class Handler
+  fun ref apply(line: String, prompt: Promise[String]) =>
+    let p = Promise[String]
+    // BUG: Can't change the flatten_next
+    p.flatten_next[String]({ (x: String) => Promise[String] })
+
+
+actor Main
+  new create(env: Env) =>
+    // BUG: Can't change this
+    let term = FlattenNextProbe(Handler)
\ No newline at end of file