diff --git a/blue.asm b/blue.asm
index ee680b2..cbca4d3 100644
--- a/blue.asm
+++ b/blue.asm
@@ -46,6 +46,7 @@ entry $
 	syscall
 
 	mov	rdi, rax
+	mov	rsi, program_code
 	mov	eax, program_code.entry_offset
 	mov	ecx, program_code.length
 	call	elf_binary_write
diff --git a/elf.inc b/elf.inc
index 1e32c2e..3a3c0ab 100644
--- a/elf.inc
+++ b/elf.inc
@@ -101,9 +101,9 @@ shstrtab_section_header:
 	.length = $ - shstrtab_section_header
 	assert .length = 0x40
 	
-elf_binary_length = $ - elf_binary
+elf_binary_wrapper_length = $ - elf_binary
 elf_binary_headers_length = elf_header.length + program_header.length
-elf_binary_section_headers_length = elf_binary_length - elf_binary_section_headers
+elf_binary_section_headers_length = $ - elf_binary_section_headers
 elf_binary_section_headers_offset = elf_binary_section_headers - elf_binary 
 
 segment readable executable
@@ -145,11 +145,14 @@ elf_binary_calculate_fields:
 	ret
 ;
 ; expects
+;	- program code start in rsi
 ; 	- program code entry offset in eax
 ;	- program code length in ecx
 ;	- file descriptor in edi
 ;
 elf_binary_write:
+	push	rsi
+	push	rcx
 	push	rdi
 	call	elf_binary_calculate_fields
 	pop	rdi
@@ -159,8 +162,9 @@ elf_binary_write:
 	mov	eax, SYS_WRITE
 	syscall
 
-	mov	rsi, program_code
-	mov	rdx, program_code.length
+	pop	rcx
+	pop	rsi
+	mov	edx, ecx
 	mov	eax, SYS_WRITE
 	syscall
 
@@ -175,5 +179,3 @@ elf_binary_write:
 	syscall
 
 	ret
-
-	
diff --git a/elf_test_hello_world.asm b/elf_test_hello_world.asm
index 86ebad7..2b125f8 100644
--- a/elf_test_hello_world.asm
+++ b/elf_test_hello_world.asm
@@ -5,6 +5,12 @@ include "elf.inc"
 
 segment readable writeable
 
+fstat_buffer:
+	rb	48
+	.file_size:
+	rq	1
+	rb	88
+
 program_code:
 	.entry_offset = $ - program_code
 	db	0x48, 0xc7, 0xc0	; mov rax, 1 - sys_write
@@ -28,6 +34,10 @@ program_code:
 
 segment readable executable
 
+expected_output_size = elf_binary_wrapper_length + program_code.length
+
+assert expected_output_size = 384
+
 output_file:
 	db	"elf_test_hello_world.out"
 	db	0x00
@@ -44,9 +54,17 @@ entry $
 	syscall
 
 	mov	rdi, rax
+	mov	rsi, program_code
 	mov	eax, program_code.entry_offset
 	mov	ecx, program_code.length
 	call	elf_binary_write
+
+	mov	rsi, fstat_buffer
+	mov	eax, SYS_FSTAT
+	syscall
+	
+	cmp	qword [fstat_buffer.file_size], expected_output_size
+	jne	failure
 	
 	mov	eax, SYS_CLOSE
 	syscall
@@ -56,3 +74,8 @@ entry $
     	xor 	rdx, rdx
 	mov	eax, SYS_EXECVE
     	syscall
+
+failure:
+	mov	rdi, 1
+	mov	eax, SYS_EXIT
+	syscall
diff --git a/linux.inc b/linux.inc
index ffcfd3a..4ecc697 100644
--- a/linux.inc
+++ b/linux.inc
@@ -2,5 +2,6 @@
 SYS_WRITE 	= 1
 SYS_OPEN 	= 2
 SYS_CLOSE 	= 3
+SYS_FSTAT	= 5
 SYS_EXECVE 	= 59
 SYS_EXIT 	= 60