diff --git a/ports/esp32/machine_rtc.c b/ports/esp32/machine_rtc.c
index f7b3ae66f2..cbbfb4b84c 100644
--- a/ports/esp32/machine_rtc.c
+++ b/ports/esp32/machine_rtc.c
@@ -60,14 +60,24 @@ typedef struct _machine_rtc_obj_t {
 #define MICROPY_HW_RTC_USER_MEM_MAX     2048
 #endif
 
+// A board can enable MICROPY_HW_RTC_MEM_INIT_ALWAYS to always clear out RTC memory on boot.
+// Defaults to RTC_NOINIT_ATTR so the user memory survives WDT resets and the like.
+#if MICROPY_HW_RTC_MEM_INIT_ALWAYS
+#define _USER_MEM_ATTR RTC_DATA_ATTR
+#else
+#define _USER_MEM_ATTR RTC_NOINIT_ATTR
+#endif
+
 // Optionally compile user memory functionality if the size of memory is greater than 0
 #if MICROPY_HW_RTC_USER_MEM_MAX > 0
 #define MEM_MAGIC           0x75507921
-RTC_DATA_ATTR uint32_t rtc_user_mem_magic;
-RTC_DATA_ATTR uint16_t rtc_user_mem_len;
-RTC_DATA_ATTR uint8_t rtc_user_mem_data[MICROPY_HW_RTC_USER_MEM_MAX];
+_USER_MEM_ATTR uint32_t rtc_user_mem_magic;
+_USER_MEM_ATTR uint16_t rtc_user_mem_len;
+_USER_MEM_ATTR uint8_t rtc_user_mem_data[MICROPY_HW_RTC_USER_MEM_MAX];
 #endif
 
+#undef _USER_MEM_ATTR
+
 // singleton RTC object
 STATIC const machine_rtc_obj_t machine_rtc_obj = {{&machine_rtc_type}};
 
@@ -80,6 +90,13 @@ STATIC mp_obj_t machine_rtc_make_new(const mp_obj_type_t *type, size_t n_args, s
     // check arguments
     mp_arg_check_num(n_args, n_kw, 0, 0, false);
 
+    #if MICROPY_HW_RTC_USER_MEM_MAX > 0
+    if (rtc_user_mem_magic != MEM_MAGIC) {
+        rtc_user_mem_magic = MEM_MAGIC;
+        rtc_user_mem_len = 0;
+    }
+    #endif
+
     // return constant object
     return (mp_obj_t)&machine_rtc_obj;
 }
@@ -130,13 +147,6 @@ STATIC mp_obj_t machine_rtc_init(mp_obj_t self_in, mp_obj_t date) {
     mp_obj_t args[2] = {self_in, date};
     machine_rtc_datetime_helper(2, args);
 
-    #if MICROPY_HW_RTC_USER_MEM_MAX > 0
-    if (rtc_user_mem_magic != MEM_MAGIC) {
-        rtc_user_mem_magic = MEM_MAGIC;
-        rtc_user_mem_len = 0;
-    }
-    #endif
-
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(machine_rtc_init_obj, machine_rtc_init);