diff --git a/core/embed/bootloader/messages.c b/core/embed/bootloader/messages.c
index 96c2f3b48b..b542e4e94b 100644
--- a/core/embed/bootloader/messages.c
+++ b/core/embed/bootloader/messages.c
@@ -721,12 +721,14 @@ int process_msg_FirmwareUpload(uint8_t iface_num, uint32_t msg_size,
   }
 
   // buffer with the received data
-  const uint32_t *quadword_ptr = (const uint32_t *)CHUNK_BUFFER_PTR;
+  const uint32_t *src = (const uint32_t *)CHUNK_BUFFER_PTR;
   // number of received bytes
   uint32_t bytes_remaining = chunk_size;
   // offset into the FIRMWARE_AREA part of the flash
   uint32_t write_offset = firmware_block * IMAGE_CHUNK_SIZE;
 
+  ensure(chunk_size % FLASH_BLOCK_SIZE == 0, NULL);
+
   while (bytes_remaining > 0) {
     // erase flash before writing
     uint32_t bytes_erased = 0;
@@ -748,12 +750,10 @@ int process_msg_FirmwareUpload(uint8_t iface_num, uint32_t msg_size,
 
     ensure(flash_unlock_write(), NULL);
     while (write_offset < write_end) {
-      // write a quad word (16 bytes) to the flash
-      ensure(
-          flash_area_write_quadword(&FIRMWARE_AREA, write_offset, quadword_ptr),
-          NULL);
-      write_offset += 4 * sizeof(uint32_t);
-      quadword_ptr += 4;
+      // write a block to the flash
+      ensure(flash_area_write_block(&FIRMWARE_AREA, write_offset, src), NULL);
+      write_offset += FLASH_BLOCK_SIZE;
+      src += FLASH_BLOCK_WORDS;
     }
     ensure(flash_lock_write(), NULL);
 
diff --git a/core/embed/bootloader_ci/messages.c b/core/embed/bootloader_ci/messages.c
index 3f5a92f83c..aba59ae7de 100644
--- a/core/embed/bootloader_ci/messages.c
+++ b/core/embed/bootloader_ci/messages.c
@@ -615,11 +615,12 @@ int process_msg_FirmwareUpload(uint8_t iface_num, uint32_t msg_size,
 
   const uint32_t *const src = (const uint32_t *const)chunk_buffer;
 
-  for (int i = 0; i < chunk_size / (sizeof(uint32_t) * 4); i++) {
-    ensure(flash_area_write_quadword(
+  ensure(chunk_size % FLASH_BLOCK_SIZE == 0, NULL);
+  for (int i = 0; i < chunk_size / FLASH_BLOCK_SIZE; i++) {
+    ensure(flash_area_write_block(
                &FIRMWARE_AREA,
-               firmware_block * IMAGE_CHUNK_SIZE + i * 4 * sizeof(uint32_t),
-               &src[4 * i]),
+               firmware_block * IMAGE_CHUNK_SIZE + i * FLASH_BLOCK_SIZE,
+               &src[FLASH_BLOCK_WORDS * i]),
            NULL);
   }
 
diff --git a/core/embed/reflash/main.c b/core/embed/reflash/main.c
index 5f7a3de2d8..d1f266d62e 100644
--- a/core/embed/reflash/main.c
+++ b/core/embed/reflash/main.c
@@ -40,6 +40,7 @@ static void flash_from_sdcard(const flash_area_t* area, uint32_t source,
                               uint32_t length) {
   static uint32_t buf[SDCARD_BLOCK_SIZE / sizeof(uint32_t)];
 
+  _Static_assert(SDCARD_BLOCK_SIZE % FLASH_BLOCK_SIZE == 0);
   ensure(sectrue * (source % SDCARD_BLOCK_SIZE == 0),
          "source not a multiple of block size");
   ensure(sectrue * (length % SDCARD_BLOCK_SIZE == 0),
@@ -51,10 +52,11 @@ static void flash_from_sdcard(const flash_area_t* area, uint32_t source,
     ensure(sdcard_read_blocks(buf, i + source / SDCARD_BLOCK_SIZE, 1),
            "sdcard_read_blocks");
 
-    for (uint32_t j = 0; j < SDCARD_BLOCK_SIZE / (sizeof(uint32_t) * 4); j++) {
-      ensure(flash_area_write_quadword(
-                 area, i * SDCARD_BLOCK_SIZE + j * 4 * sizeof(uint32_t),
-                 &buf[j * 4]),
+    for (uint32_t j = 0; j < SDCARD_BLOCK_SIZE / FLASH_BLOCK_SIZE)
+      ; j++) {
+      ensure(flash_area_write_block(
+                 area, i * SDCARD_BLOCK_SIZE + j * FLASH_BLOCK_SIZE,
+                 &buf[j * FLASH_BLOCK_WORDS]),
              NULL);
     }
   }
diff --git a/storage/flash_common.c b/storage/flash_common.c
index 78fa17e07d..54e1caf371 100644
--- a/storage/flash_common.c
+++ b/storage/flash_common.c
@@ -1,3 +1,5 @@
+#include "flash_common.h"
+
 #include "flash.h"
 
 secbool flash_write_byte(uint16_t sector, uint32_t offset, uint8_t data);
@@ -121,16 +123,28 @@ secbool flash_area_write_word(const flash_area_t *area, uint32_t offset,
   return flash_write_word(sector, sector_offset, data);
 }
 
-secbool flash_area_write_quadword(const flash_area_t *area, uint32_t offset,
-                                  const uint32_t *data) {
-  if (offset % 16 != 0) {
+secbool flash_area_write_block(const flash_area_t *area, uint32_t offset,
+                               const flash_block_t block) {
+  if (!FLASH_IS_ALIGNED(offset)) {
     return secfalse;
   }
-  for (int i = 0; i < 4; i++) {
-    if (sectrue !=
-        flash_area_write_word(area, offset + i * sizeof(uint32_t), data[i])) {
+
+  uint16_t sector;
+  uint32_t sector_offset;
+  if (sectrue != get_sector_and_offset(area, offset, &sector, &sector_offset)) {
+    return secfalse;
+  }
+
+#if FLASH_BLOCK_WORDS == 1
+  return flash_write_word(sector, sector_offset, block);
+#else
+  for (int i = 0; i < FLASH_BLOCK_WORDS; i++) {
+    if (sectrue != flash_write_word(sector,
+                                    sector_offset + i * sizeof(uint32_t),
+                                    block[i])) {
       return secfalse;
     }
   }
   return sectrue;
+#endif
 }
diff --git a/storage/flash_common.h b/storage/flash_common.h
index b8cac2b55f..0d38752d85 100644
--- a/storage/flash_common.h
+++ b/storage/flash_common.h
@@ -14,6 +14,14 @@ typedef struct {
   uint8_t num_subareas;
 } flash_area_t;
 
+#define FLASH_BLOCK_SIZE (sizeof(uint32_t) * FLASH_BLOCK_WORDS)
+
+#if FLASH_BLOCK_WORDS == 1
+typedef uint32_t flash_block_t;
+#else
+typedef uint32_t flash_block_t[FLASH_BLOCK_WORDS];
+#endif
+
 void flash_init(void);
 
 secbool __wur flash_unlock_write(void);
@@ -39,7 +47,7 @@ secbool __wur flash_area_write_byte(const flash_area_t *area, uint32_t offset,
 secbool __wur flash_area_write_word(const flash_area_t *area, uint32_t offset,
                                     uint32_t data);
 #endif
-secbool __wur flash_area_write_quadword(const flash_area_t *area,
-                                        uint32_t offset, const uint32_t *data);
+secbool __wur flash_area_write_block(const flash_area_t *area, uint32_t offset,
+                                     const flash_block_t block);
 
 #endif