diff --git a/loader/inc/memory.h b/loader/inc/memory.h
index e60fb76..5ceeab4 100644
--- a/loader/inc/memory.h
+++ b/loader/inc/memory.h
@@ -32,7 +32,7 @@
 
 void mem_read_memory(unsigned int* address, uint8_t* buffer, uint32_t length);
 void mem_write_word(unsigned int* address, uint32_t word);
-void mem_write_sector(unsigned int* address, uint8_t* buffer);
+void mem_write_sector(unsigned int* address, unsigned int* buffer);
 void mem_erase_sector(unsigned int* address);
 
 
diff --git a/loader/src/flash.c b/loader/src/flash.c
index 2d48a13..bcd610c 100644
--- a/loader/src/flash.c
+++ b/loader/src/flash.c
@@ -155,9 +155,9 @@ void update_checksums(const uint32_t* nvm, uint32_t* ram, int sectors)
   int i;
 
   for (i = 0; i < sectors; i++,
-         nvm += SECTOR_SIZE, ram += SECTOR_SIZE) {
+         nvm += 64, ram += 64) {
     mem_erase_sector((unsigned int*)nvm);
-    mem_write_sector((unsigned int*)nvm, (uint8_t*)ram);
+    mem_write_sector((unsigned int*)nvm, (unsigned int*)ram);
 
     kick_the_watchdog();
   }
@@ -182,7 +182,7 @@ uint32_t check_and_repair_memory(void)
 
   /* foreach sector */
   for (i = 0; i < D1_SECTORS; i++,
-         address1 += SECTOR_SIZE, address2 += SECTOR_SIZE) {
+         address1 += 64, address2 += 64) {
     /* calculate checksums */
     check1 = checksum_sector(address1);
     check2 = checksum_sector(address2);
@@ -196,7 +196,7 @@ uint32_t check_and_repair_memory(void)
                (check2 == d2_checksums_ram[i])) {
       /* restore d1 */
       mem_erase_sector(address1);
-      mem_write_sector(address1, (uint8_t*)address2);
+      mem_write_sector(address1, address2);
 
       /* update d1 checksum */
       d1_checksums_ram[i] = check2;
@@ -209,7 +209,7 @@ uint32_t check_and_repair_memory(void)
                (check2 != d2_checksums_ram[i])) {
       /* restore d2 */
       mem_erase_sector(address2);
-      mem_write_sector(address2, (uint8_t*)address1);
+      mem_write_sector(address2, address1);
 
       /* update d2 checksum */
       d2_checksums_ram[i] = check1;
@@ -222,7 +222,7 @@ uint32_t check_and_repair_memory(void)
       /* both bad, restore d2 and calculate both checksums */
       /* restore d2 */
       mem_erase_sector(address2);
-      mem_write_sector(address2, (uint8_t*)address1);
+      mem_write_sector(address2, address1);
 
       /* update both checksums */
       d1_checksums_ram[i] = check1;
diff --git a/loader/src/memory.c b/loader/src/memory.c
index d3ef172..8e77d17 100644
--- a/loader/src/memory.c
+++ b/loader/src/memory.c
@@ -86,10 +86,9 @@ void mem_write_word(unsigned int* address, uint32_t word)
 /**
  * Write 256-byte sector. Address must be sector aligned
  */
-void mem_write_sector(unsigned int* address, uint8_t* buffer)
+void mem_write_sector(unsigned int* address, unsigned int* buffer)
 {
   int i;
-  uint8_t tempbuf[0x40];
 
 #ifdef FIX_ERRATA_REV_C_FLASH_10804
   /* save CTRLB and disable cache */
@@ -103,9 +102,12 @@ void mem_write_sector(unsigned int* address, uint8_t* buffer)
   for (i = 0; i < 4; i++) {     /* write by page */
     /* write address */
     NVMCTRL->ADDR.reg = (uint32_t)(address) >> 1;
+
     /* write page. length must be multiple of two */
-    memcpy((void*)tempbuf, buffer, 0x40);
-    memcpy((void*)address, tempbuf, 0x40);
+    for (int j = 0; j < 0x10; j++) {
+      address[j] = buffer[j];
+    }
+
     /* unlock */
     NVMCTRL->CTRLA.reg = NVMCTRL_CTRLA_CMDEX_KEY | NVMCTRL_CTRLA_CMD_UR;
     /* write page */
@@ -115,8 +117,8 @@ void mem_write_sector(unsigned int* address, uint8_t* buffer)
     NVMCTRL->CTRLA.reg = NVMCTRL_CTRLA_CMDEX_KEY | NVMCTRL_CTRLA_CMD_LR;
 
     /* next page */
-    address += 0x40;
-    buffer  += 0x40;
+    address += 0x10;
+    buffer  += 0x10;
   }