diff --git a/examples/deep_sleep.rs b/examples/deep_sleep.rs
index b8f39c6cc4b..17b60565a39 100644
--- a/examples/deep_sleep.rs
+++ b/examples/deep_sleep.rs
@@ -10,7 +10,7 @@ use esp_idf_hal::sleep::DeepSleep;
 use esp_idf_hal::sleep::Sleep;
 use esp_idf_hal::sleep::WakeupSource;
 use std::thread;
-use std::time::Duration;
+use core::time::Duration;
 
 fn main() -> anyhow::Result<()> {
     esp_idf_sys::link_patches();
diff --git a/examples/light_sleep.rs b/examples/light_sleep.rs
index 2d976ce84ef..63093841cdc 100644
--- a/examples/light_sleep.rs
+++ b/examples/light_sleep.rs
@@ -8,7 +8,7 @@ use esp_idf_hal::sleep::LightSleep;
 use esp_idf_hal::sleep::Sleep;
 use esp_idf_hal::sleep::WakeupSource;
 use std::thread;
-use std::time::Duration;
+use core::time::Duration;
 use std::time::Instant;
 
 fn print_wakeup_result(time_before: Instant) {
diff --git a/src/sleep.rs b/src/sleep.rs
index 01a4f0b9dca..38167bafae7 100644
--- a/src/sleep.rs
+++ b/src/sleep.rs
@@ -3,10 +3,14 @@
 //! Currently implemented Timer and UART wakeup sources.
 
 use esp_idf_sys::*;
-use std::time::Duration;
+use core::time::Duration;
 
-#[derive(Debug)]
+const MAX_WAKEUP_SOURCES: usize = 10;
+
+#[derive(Default, Debug)]
 pub enum WakeupSource {
+    #[default]
+    None,
     Timer { dur: Duration },
     Uart { uart_num: i32, threshold: i32 },
     // TODO: add more sources
@@ -15,6 +19,7 @@ pub enum WakeupSource {
 impl WakeupSource {
     pub fn apply(&self) -> Result<(), EspError> {
         match *self {
+            WakeupSource::None => {}
             WakeupSource::Timer { dur } => {
                 esp!(unsafe { esp_sleep_enable_timer_wakeup(dur.as_micros() as u64) })?;
             }
@@ -48,7 +53,8 @@ pub trait Sleep {
 
 #[derive(Default, Debug)]
 pub struct LightSleep {
-    wakeup_sources: Vec<WakeupSource>,
+    wakeup_sources: [WakeupSource; MAX_WAKEUP_SOURCES],
+    n_wakeup_sources: usize,
 }
 
 impl LightSleep {
@@ -63,7 +69,11 @@ impl LightSleep {
 
 impl Sleep for LightSleep {
     fn add_wakeup_source(&mut self, wakeup: WakeupSource) -> Result<(), EspError> {
-        self.wakeup_sources.push(wakeup);
+        if self.n_wakeup_sources >= MAX_WAKEUP_SOURCES {
+            return Err(EspError::from_infallible::<ESP_FAIL>())
+        }
+        self.wakeup_sources[self.n_wakeup_sources] = wakeup;
+        self.n_wakeup_sources += 1;
         Ok(())
     }
 
@@ -77,7 +87,8 @@ impl Sleep for LightSleep {
 
 #[derive(Default, Debug)]
 pub struct DeepSleep {
-    wakeup_sources: Vec<WakeupSource>,
+    wakeup_sources: [WakeupSource; MAX_WAKEUP_SOURCES],
+    n_wakeup_sources: usize,
 }
 
 impl DeepSleep {
@@ -95,12 +106,18 @@ impl Sleep for DeepSleep {
         if matches!(wakeup, WakeupSource::Uart { .. }) {
             return Err(EspError::from_infallible::<ESP_ERR_INVALID_ARG>());
         }
-        self.wakeup_sources.push(wakeup);
+
+        if self.n_wakeup_sources >= MAX_WAKEUP_SOURCES {
+            return Err(EspError::from_infallible::<ESP_FAIL>());
+        }
+        self.wakeup_sources[self.n_wakeup_sources] = wakeup;
+        self.n_wakeup_sources += 1;
+
         Ok(())
     }
 
     fn sleep(&self) -> Result<(), EspError> {
-        self.apply_wakeup_sources(&self.wakeup_sources)?;
+        self.apply_wakeup_sources(&self.wakeup_sources[0..self.n_wakeup_sources])?;
 
         unsafe { esp_deep_sleep_start() };
         #[allow(unreachable_code)]