diff --git a/Makefile b/Makefile
index 94114bc..50c28b6 100644
--- a/Makefile
+++ b/Makefile
@@ -7,9 +7,7 @@ PYTHON = python3
 all: ponydos.img
 
 ponydos.img: ponydos.bin wallpaper.bin
-	rw -i /dev/zero -o $@ -c 1440K
-	rw -i ponydos.bin -o $@
-	rw -i wallpaper.bin -o $@ -O 1024
+	$(PYTHON) assemble_floppy.py $@ ponydos.bin wallpaper.bin
 
 .asm.bin:
 	$(NASM) -fbin -o $@ $<
diff --git a/assemble_floppy.py b/assemble_floppy.py
new file mode 100644
index 0000000..44e0f53
--- /dev/null
+++ b/assemble_floppy.py
@@ -0,0 +1,63 @@
+import sys
+import os.path
+
+floppy_bytes = 1440 * 1024
+sector_bytes = 512
+dirent_bytes = 32
+
+floppy = bytearray()
+
+def extend_padded(buffer, alignment, data):
+	padding_len = (alignment - len(data)) % alignment
+	buffer.extend(data)
+	buffer.extend(bytes(padding_len))
+
+if len(sys.argv) < 3:
+	print(f'Usage: {sys.argv[0]} disk.img bootsector.bin files…', file=sys.stderr)
+	sys.exit(1)
+
+output_path = sys.argv[1]
+bootsector_path = sys.argv[2]
+files_paths = sys.argv[3:]
+
+with open(bootsector_path, 'rb') as f:
+	bootsector = f.read()
+assert len(bootsector) == sector_bytes
+floppy.extend(bootsector)
+
+files = []
+directory = bytearray()
+
+for file_path in files_paths:
+	with open(file_path, 'rb') as f:
+		file_contents = f.read()
+	assert len(file_contents) <= 128 * sector_bytes # 128 sector files
+	files.append(file_contents)
+
+	# dirent:
+	#  2 bytes size in 512B sectors, 0 for end of listing
+	#  30 bytes null-terminated name
+	sectors = (len(file_contents) + sector_bytes - 1) // sector_bytes
+	file_name = os.path.basename(file_path).encode() + b'\0'
+	assert len(file_name) <= 30
+	dirent = bytes([sectors & 0xff, sectors >> 8]) + file_name
+	extend_padded(directory, dirent_bytes, dirent)
+
+# Add a zero dirent to mark the end of the directory
+# (and the start of the consulate)
+directory.extend(bytes(dirent_bytes))
+
+assert len(directory) <= sector_bytes
+
+extend_padded(floppy, sector_bytes, directory)
+
+for file_contents in files:
+	extend_padded(floppy, sector_bytes, file_contents)
+
+assert len(floppy) <= floppy_bytes
+
+output = bytearray()
+extend_padded(output, floppy_bytes, floppy)
+
+with open(output_path, 'wb') as f:
+	f.write(output)
diff --git a/filesystem.asm b/filesystem.asm
deleted file mode 100644
index 18edef4..0000000
--- a/filesystem.asm
+++ /dev/null
@@ -1,14 +0,0 @@
-; TODO: have tooling for this
-
-; 128 sector files, starting at 2
-
-; dirent:
-;  2 bytes size in 512B sectors, 0 for end of listing
-;  30 bytes null-terminated name
-
-wallpaper:
-	dw 8
-	db 'wallpaper.bin', 0
-	times 512+32-($-$$) db 0
-
-times 1024-($-$$) db 0
\ No newline at end of file
diff --git a/ponydos.asm b/ponydos.asm
index d1c7532..3934af8 100644
--- a/ponydos.asm
+++ b/ponydos.asm
@@ -441,8 +441,6 @@ times 510-($-$$) db 0
 db 0x55
 db 0xaa
 
-%include "filesystem.asm"
-
 ; ------------------------------------------------------------------
 ; Zero-initialized variables
 ; ------------------------------------------------------------------
@@ -459,4 +457,4 @@ mouse_row resw 1
 
 boot_disk resb 1
 
-_bss_end:
\ No newline at end of file
+_bss_end: