diff --git a/components/esp_system/sleep_modes.c b/components/esp_system/sleep_modes.c
index 521fb91a71..cdc9cf8e69 100644
--- a/components/esp_system/sleep_modes.c
+++ b/components/esp_system/sleep_modes.c
@@ -1280,10 +1280,14 @@ static uint32_t get_power_down_flags(void)
 #if SOC_RTC_SLOW_MEM_SUPPORTED && SOC_ULP_SUPPORTED
     // Labels are defined in the linker script
     extern int _rtc_slow_length;
+    /**
+     * Compiler considers "(size_t) &_rtc_slow_length > 0" to always be true.
+     * So use a volatile variable to prevent compiler from doing this optimization.
+     */
+    volatile size_t rtc_slow_mem_used = (size_t)&_rtc_slow_length;
 
     if ((s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] == ESP_PD_OPTION_AUTO) &&
-            ((size_t) &_rtc_slow_length > 0 ||
-             (s_config.wakeup_triggers & RTC_ULP_TRIG_EN))) {
+            (rtc_slow_mem_used > 0 || (s_config.wakeup_triggers & RTC_ULP_TRIG_EN))) {
         s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] = ESP_PD_OPTION_ON;
     }
 #endif