diff --git a/flash.c b/flash.c
index 76ef6d4..233eb3a 100644
--- a/flash.c
+++ b/flash.c
@@ -94,6 +94,8 @@ uintptr_t allocate_free_addr(uint16_t size) {
         uintptr_t addr_alg = base & -FLASH_SECTOR_SIZE; //start address of sector
         uintptr_t potential_addr = base-real_size;
         next_base = flash_read_uintptr(base);
+        //printf("nb %x %x %x %x\r\n",base,next_base,addr_alg,potential_addr);
+        //printf("fid %x\r\n",flash_read_uint16(next_base+sizeof(uintptr_t)));
         if (next_base == 0x0) { //we are at the end
             //now we check if we fit in the current sector
             if (addr_alg <= potential_addr) //it fits in the current sector
@@ -111,7 +113,7 @@ uintptr_t allocate_free_addr(uint16_t size) {
             return 0x0;
         }
         //we check if |base-(next_addr+size_next_addr)| > |base-potential_addr| only if fid != 1xxx (not size blocked)
-        else if (addr_alg <= potential_addr && base-(next_base+flash_read_uint16(next_base+sizeof(uintptr_t)+sizeof(uint16_t))) > base-potential_addr && flash_read_uint16(next_base+sizeof(uintptr_t)+sizeof(uint16_t)) & 0x1000 != 0x1000) {
+        else if (addr_alg <= potential_addr && base-(next_base+flash_read_uint16(next_base+sizeof(uintptr_t)+sizeof(uint16_t))+2*sizeof(uint16_t)) > base-potential_addr && flash_read_uint16(next_base+sizeof(uintptr_t)) & 0x1000 != 0x1000) {
             flash_program_uintptr(potential_addr, next_base);
             flash_program_uintptr(base, potential_addr);
             return potential_addr;
@@ -122,14 +124,17 @@ uintptr_t allocate_free_addr(uint16_t size) {
 
 int flash_clear_file(file_t *file) {
     uintptr_t prev_addr = (uintptr_t)(file->data+flash_read_uint16((uintptr_t)file->data)+sizeof(uint16_t));
-    uintptr_t base_addr = (uintptr_t)file->data-sizeof(uintptr_t);
+    uintptr_t base_addr = (uintptr_t)(file->data-sizeof(uintptr_t)-sizeof(uint16_t));
     uintptr_t next_addr = flash_read_uintptr(base_addr);
+    //printf("nc %x %x %x\r\n",prev_addr,base_addr,next_addr);
     flash_program_uintptr(prev_addr, next_addr);
     flash_program_halfword((uintptr_t)file->data, 0);
     return 0;
 }
 
 int flash_write_data_to_file(file_t *file, const uint8_t *data, uint16_t len) {
+    if (!file)
+        return HSM_ERR_NULL_PARAM;
     if (len > FLASH_SECTOR_SIZE)
         return HSM_ERR_NO_MEMORY;
     if (file->data) { //already in flash
@@ -144,6 +149,7 @@ int flash_write_data_to_file(file_t *file, const uint8_t *data, uint16_t len) {
         }
     }
     uintptr_t new_addr = allocate_free_addr(len);
+    //printf("na %x\r\n",new_addr);
     if (new_addr == 0x0) 
         return HSM_ERR_NO_MEMORY;
     file->data = (uint8_t *)new_addr+sizeof(uintptr_t)+sizeof(uint16_t); //next addr+fid