diff --git a/lldb/source/Core/IOHandler.cpp b/lldb/source/Core/IOHandler.cpp
--- a/lldb/source/Core/IOHandler.cpp
+++ b/lldb/source/Core/IOHandler.cpp
@@ -125,6 +125,8 @@
     std::lock_guard<std::recursive_mutex> guard(m_mutex);
     if (m_top)
       m_top->PrintAsync(stream, s, len);
+    else
+      stream->Write(s, len);
   }
 }
 
diff --git a/lldb/test/Shell/Commands/command-thread-select.test b/lldb/test/Shell/Commands/command-thread-select.test
new file mode 100644
--- /dev/null
+++ b/lldb/test/Shell/Commands/command-thread-select.test
@@ -0,0 +1,17 @@
+# RUN: %clang_host -g %S/Inputs/main.c -o %t
+# RUN: %lldb %t -s %s -o exit | FileCheck %s
+
+b main
+# CHECK-LABEL: b main
+# CHECK: Breakpoint 1: where = {{.*}}`main
+
+run
+# CHECK-LABEL: run
+# CHECK: Process {{.*}} stopped
+# CHECK: stop reason = breakpoint 1
+# CHECK:   frame #0: {{.*}}`main at main.c
+
+thread select 1
+# CHECK-LABEL: thread select 1
+# CHECK: stop reason = breakpoint 1
+# CHECK:   frame #0: {{.*}}`main at main.c