diff --git a/ports/rp2/mpconfigport.h b/ports/rp2/mpconfigport.h
index 1cc9b9616..d7f322570 100644
--- a/ports/rp2/mpconfigport.h
+++ b/ports/rp2/mpconfigport.h
@@ -89,9 +89,11 @@
 // Fine control over Python builtins, classes, modules, etc
 #define MICROPY_PY_BUILTINS_HELP_TEXT           rp2_help_text
 #define MICROPY_PY_SYS_PLATFORM                 "rp2"
+#ifndef MICROPY_PY_THREAD
 #define MICROPY_PY_THREAD                       (1)
 #define MICROPY_PY_THREAD_GIL                   (0)
 #define MICROPY_THREAD_YIELD()                  mp_handle_pending(true)
+#endif
 
 // Extended modules
 #define MICROPY_EPOCH_IS_1970                   (1)
diff --git a/ports/rp2/mphalport.h b/ports/rp2/mphalport.h
index 9feace2f4..f0be93d8e 100644
--- a/ports/rp2/mphalport.h
+++ b/ports/rp2/mphalport.h
@@ -36,9 +36,14 @@
 #define SYSTICK_MAX (0xffffff)
 #define MICROPY_HW_USB_CDC_TX_TIMEOUT (500)
 
+#if MICROPY_PY_THREAD
 // Entering a critical section.
 #define MICROPY_BEGIN_ATOMIC_SECTION()     mp_thread_begin_atomic_section()
 #define MICROPY_END_ATOMIC_SECTION(state)  mp_thread_end_atomic_section(state)
+#else
+#define MICROPY_BEGIN_ATOMIC_SECTION()     save_and_disable_interrupts()
+#define MICROPY_END_ATOMIC_SECTION(state)  restore_interrupts(state)
+#endif
 
 #define MICROPY_PY_PENDSV_ENTER   pendsv_suspend()
 #define MICROPY_PY_PENDSV_EXIT    pendsv_resume()