diff --git a/lldb/test/API/commands/gui/expand-threads-tree/Makefile b/lldb/test/API/commands/gui/expand-threads-tree/Makefile
index 0c11fbdd8669..566938ca0cc4 100644
--- a/lldb/test/API/commands/gui/expand-threads-tree/Makefile
+++ b/lldb/test/API/commands/gui/expand-threads-tree/Makefile
@@ -1,3 +1,3 @@
-C_SOURCES := main.c
+CXX_SOURCES := main.cpp
 ENABLE_THREADS := YES
 include Makefile.rules
diff --git a/lldb/test/API/commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py b/lldb/test/API/commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py
index c3ec4b285ecd..9eed5b0ef6c3 100644
--- a/lldb/test/API/commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py
+++ b/lldb/test/API/commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py
@@ -22,7 +22,7 @@ class TestGuiExpandThreadsTree(PExpectTest):
         self.build()
 
         self.launch(executable=self.getBuildArtifact("a.out"), dimensions=(100,500))
-        self.expect("breakpoint set -r thread_start_routine", substrs=["Breakpoint 1", "address ="])
+        self.expect("breakpoint set -n break_here", substrs=["Breakpoint 1", "address ="])
         self.expect("run", substrs=["stop reason ="])
 
         escape_key = chr(27).encode()
@@ -33,7 +33,7 @@ class TestGuiExpandThreadsTree(PExpectTest):
         self.child.expect_exact("Threads")
 
         # The thread running thread_start_routine should be expanded.
-        self.child.expect_exact("frame #0: thread_start_routine")
+        self.child.expect_exact("frame #0: break_here")
 
         # Exit GUI.
         self.child.send(escape_key)
diff --git a/lldb/test/API/commands/gui/expand-threads-tree/main.c b/lldb/test/API/commands/gui/expand-threads-tree/main.c
deleted file mode 100644
index 32e6d17c799a..000000000000
--- a/lldb/test/API/commands/gui/expand-threads-tree/main.c
+++ /dev/null
@@ -1,10 +0,0 @@
-#include <pthread.h>
-
-void *thread_start_routine(void *arg) { return NULL; }
-
-int main() {
-  pthread_t thread;
-  pthread_create(&thread, NULL, thread_start_routine, NULL);
-  pthread_join(thread, NULL);
-  return 0;
-}
diff --git a/lldb/test/API/commands/gui/expand-threads-tree/main.cpp b/lldb/test/API/commands/gui/expand-threads-tree/main.cpp
new file mode 100644
index 000000000000..5a7cbb78563c
--- /dev/null
+++ b/lldb/test/API/commands/gui/expand-threads-tree/main.cpp
@@ -0,0 +1,24 @@
+#include "pseudo_barrier.h"
+#include <thread>
+
+
+pseudo_barrier_t barrier_before;
+pseudo_barrier_t barrier_after;
+
+void break_here() {}
+
+void thread_func() {
+    pseudo_barrier_wait(barrier_before);
+    break_here();
+    pseudo_barrier_wait(barrier_after);
+}
+
+int main() {
+  pseudo_barrier_init(barrier_before, 2);
+  pseudo_barrier_init(barrier_after, 2);
+  std::thread thread(thread_func);
+  pseudo_barrier_wait(barrier_before);
+  pseudo_barrier_wait(barrier_after);
+  thread.join();
+  return 0;
+}