diff --git a/cpu/stm32_common/periph/flash_common.c b/cpu/stm32_common/periph/flash_common.c
index 34f92e75f06f..61c6d8d10fd6 100644
--- a/cpu/stm32_common/periph/flash_common.c
+++ b/cpu/stm32_common/periph/flash_common.c
@@ -38,8 +38,8 @@
 
 void _unlock(void)
 {
-    DEBUG("[flash-common] unlocking the flash module\n");
     if (CNTRL_REG & CNTRL_REG_LOCK) {
+        DEBUG("[flash-common] unlocking the flash module\n");
         KEY_REG = FLASH_KEY1;
         KEY_REG = FLASH_KEY2;
     }
@@ -47,6 +47,8 @@ void _unlock(void)
 
 void _lock(void)
 {
-    DEBUG("[flash-common] locking the flash module\n");
-    CNTRL_REG |= CNTRL_REG_LOCK;
+    if (!(CNTRL_REG & CNTRL_REG_LOCK)) {
+        DEBUG("[flash-common] locking the flash module\n");
+        CNTRL_REG |= CNTRL_REG_LOCK;
+    }
 }
diff --git a/cpu/stm32_common/periph/flashpage.c b/cpu/stm32_common/periph/flashpage.c
index e4454b18183b..9bbebd36ad5f 100644
--- a/cpu/stm32_common/periph/flashpage.c
+++ b/cpu/stm32_common/periph/flashpage.c
@@ -65,6 +65,17 @@ static void _unlock_flash(void)
 #endif
 }
 
+static void _wait_for_pending_operations(void)
+{
+    DEBUG("[flashpage] waiting for any pending operation to finish\n");
+    while (FLASH->SR & FLASH_SR_BSY) {}
+
+    /* Clear 'end of operation' bit in status register */
+    if (FLASH->SR & FLASH_SR_EOP) {
+        FLASH->SR &= ~(FLASH_SR_EOP);
+    }
+}
+
 static void _erase_page(void *page_addr)
 {
 #if defined(CPU_FAM_STM32L0) || defined(CPU_FAM_STM32L1)
@@ -77,12 +88,12 @@ static void _erase_page(void *page_addr)
     stmclk_enable_hsi();
 #endif
 
-   /* unlock the flash module */
+    /* unlock the flash module */
     _unlock_flash();
 
     /* make sure no flash operation is ongoing */
-    DEBUG("[flashpage] erase: waiting for any operation to finish\n");
-    while (FLASH->SR & FLASH_SR_BSY) {}
+    _wait_for_pending_operations();
+
     /* set page erase bit and program page address */
     DEBUG("[flashpage] erase: setting the erase bit\n");
     CNTRL_REG |= FLASH_CR_PER;
@@ -97,8 +108,9 @@ static void _erase_page(void *page_addr)
     DEBUG("[flashpage] erase: trigger the page erase\n");
     CNTRL_REG |= FLASH_CR_STRT;
 #endif
-    DEBUG("[flashpage] erase: wait as long as device is busy\n");
-    while (FLASH->SR & FLASH_SR_BSY) {}
+    /* wait as long as device is busy */
+    _wait_for_pending_operations();
+
     /* reset PER bit */
     DEBUG("[flashpage] erase: resetting the page erase bit\n");
     CNTRL_REG &= ~(FLASH_CR_PER);
@@ -140,10 +152,10 @@ void flashpage_write_raw(void *target_addr, const void *data, size_t len)
     stmclk_enable_hsi();
 #endif
 
-    DEBUG("[flashpage_raw] unlocking the flash module\n");
+    /* unlock the flash module */
     _unlock_flash();
 
-    DEBUG("[flashpage] write: now writing the data\n");
+    DEBUG("[flashpage_raw] write: now writing the data\n");
 #if !(defined(CPU_FAM_STM32L0) || defined(CPU_FAM_STM32L1))
     /* set PG bit and program page to flash */
     CNTRL_REG |= FLASH_CR_PG;
@@ -151,14 +163,15 @@ void flashpage_write_raw(void *target_addr, const void *data, size_t len)
     for (size_t i = 0; i < (len / FLASHPAGE_DIV); i++) {
         DEBUG("[flashpage_raw] writing %c to %p\n", (char)data_addr[i], dst);
         *dst++ = data_addr[i];
-        while (FLASH->SR & FLASH_SR_BSY) {}
+        /* wait as long as device is busy */
+        _wait_for_pending_operations();
     }
 
     /* clear program bit again */
     CNTRL_REG &= ~(FLASH_CR_PG);
-    DEBUG("[flashpage] write: done writing data\n");
+    DEBUG("[flashpage_raw] write: done writing data\n");
 
-    DEBUG("flashpage_raw] now locking the flash module again\n");
+    /* lock the flash module again */
     _lock();
 
 #if !(defined(CPU_FAM_STM32L0) || defined(CPU_FAM_STM32L1))