diff --git a/targets/TARGET_STM/sleep.c b/targets/TARGET_STM/sleep.c
index fa4e8603b2..3dd90a3477 100644
--- a/targets/TARGET_STM/sleep.c
+++ b/targets/TARGET_STM/sleep.c
@@ -49,38 +49,16 @@ static void wait_loop(uint32_t timeout)
     return;
 }
 
+
 // On L4 platforms we've seen unstable PLL CLK configuraiton
 // when DEEP SLEEP exits just few µs after being entered
 // So we need to force MSI usage before setting clocks again
-static void ForceClockOutofDeepSleep(void)
+static void ForcePeriphOutofDeepSleep(void)
 {
-    RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
-    RCC_OscInitTypeDef RCC_OscInitStruct = {0};
     uint32_t pFLatency = 0;
-
-    /* Enable Power Control clock */
-    __HAL_RCC_PWR_CLK_ENABLE();
-
-#ifdef PWR_FLAG_VOS
-    /* Poll VOSF bit of in PWR_CSR. Wait until it is reset to 0 */
-    //while (__HAL_PWR_GET_FLAG(PWR_FLAG_VOS) != RESET) {};
-#endif
-
-    /* Get the Oscillators configuration according to the internal RCC registers */
-    HAL_RCC_GetOscConfig(&RCC_OscInitStruct);
+    RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
 #if (TARGET_STM32L4 || TARGET_STM32L1) /* MSI used for L4 */
-    /**Initializes the CPU, AHB and APB busses clocks
-    */
-    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
-    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
-    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
-    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4; // Intermediate freq, 1MHz range
-    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
-    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
-        error("clock issue\r\n");
-    }
-
     /* Get the Clocks configuration according to the internal RCC registers */
     HAL_RCC_GetClockConfig(&RCC_ClkInitStruct, &pFLatency);
 
@@ -100,16 +78,6 @@ static void ForceClockOutofDeepSleep(void)
         error("clock issue\r\n");
     }
 #else  /* HSI used on others */
-    /**Initializes the CPU, AHB and APB busses clocks
-    */
-    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
-    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
-    RCC_OscInitStruct.HSICalibrationValue = 16;
-    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
-    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
-        error("clock issue");
-    }
-
     /* Get the Clocks configuration according to the internal RCC registers */
     HAL_RCC_GetClockConfig(&RCC_ClkInitStruct, &pFLatency);
 
@@ -132,6 +100,50 @@ static void ForceClockOutofDeepSleep(void)
 #endif // TARGET_STM32L4
 }
 
+static void ForceOscOutofDeepSleep(void)
+{
+    RCC_OscInitTypeDef RCC_OscInitStruct = {0};
+
+    /* Enable Power Control clock */
+    __HAL_RCC_PWR_CLK_ENABLE();
+
+    /* Get the Oscillators configuration according to the internal RCC registers */
+    HAL_RCC_GetOscConfig(&RCC_OscInitStruct);
+
+#if (TARGET_STM32L4 || TARGET_STM32L1) /* MSI used for L4 */
+    /**Initializes the CPU, AHB and APB busses clocks
+    */
+    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
+    RCC_OscInitStruct.MSIState = RCC_MSI_ON;
+    RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
+    RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4; // Intermediate freq, 1MHz range
+    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
+    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
+        error("clock issue\r\n");
+    }
+#else  /* HSI used on others */
+    /**Initializes the CPU, AHB and APB busses clocks
+    */
+    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
+    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
+    RCC_OscInitStruct.HSICalibrationValue = 16;
+    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
+    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
+        error("clock issue");
+    }
+#endif // TARGET_STM32L4
+}
+
+/* The content of this function has been split into 2 separate functions
+   so that the involved structures are not allocated on the stack in parallel.
+   This will reduce the maximum stack usage in case on non-optimized / debug
+   compilers settings */
+static void ForceClockOutofDeepSleep(void)
+{
+    ForceOscOutofDeepSleep();
+    ForcePeriphOutofDeepSleep();
+}
+
 void hal_sleep(void)
 {
     // Disable IRQs