diff --git a/rpi-eeprom-config b/rpi-eeprom-config
index f2bbc47..a5dd19f 100755
--- a/rpi-eeprom-config
+++ b/rpi-eeprom-config
@@ -16,9 +16,6 @@ import time
 
 IMAGE_SIZE = 512 * 1024
 
-# Larger files won't with with "vcgencmd bootloader_config"
-MAX_FILE_SIZE = 2024
-ALIGN_SIZE = 4096
 BOOTCONF_TXT = 'bootconf.txt'
 BOOTCONF_SIG = 'bootconf.sig'
 PUBKEY_BIN = 'pubkey.bin'
@@ -39,6 +36,11 @@ FILE_HDR_LEN = 20
 FILENAME_LEN = 12
 TEMP_DIR = None
 
+# Modifiable files are stored in a single 4K erasable sector.
+# The max content 4076 bytes because of the file header.
+ERASE_ALIGN_SIZE = 4096
+MAX_FILE_SIZE = ERASE_ALIGN_SIZE - FILE_HDR_LEN
+
 DEBUG = False
 def debug(s):
     if DEBUG:
@@ -221,7 +223,7 @@ class ImageSection:
         self.offset = offset
         self.length = length
         self.filename = filename
-        debug("ImageSection %x %x %x %s" % (magic, offset, length, filename))
+        debug("ImageSection %x offset %d length %d %s" % (magic, offset, length, filename))
 
 class BootloaderImage(object):
     def __init__(self, filename, output=None):
@@ -250,7 +252,6 @@ class BootloaderImage(object):
         """
         offset = 0
         magic = 0
-        found = False
         while offset < IMAGE_SIZE:
             magic, length = struct.unpack_from('>LL', self._bytes, offset)
             if magic == 0x0 or magic == 0xffffffff:
@@ -262,6 +263,7 @@ class BootloaderImage(object):
             if magic == FILE_MAGIC: # Found a file
                 # Discard trailing null characters used to pad filename
                 filename = self._bytes[offset + 8: offset + FILE_HDR_LEN].decode('utf-8').replace('\0', '')
+            debug("section at %d length %d magic %08x %s" % (offset, length, magic, filename))
             self._sections.append(ImageSection(magic, offset, length, filename))
 
             offset += 8 + length # length + type
@@ -272,26 +274,46 @@ class BootloaderImage(object):
         Returns the offset, length and whether this is the last section in the
         EEPROM for a modifiable file within the image.
         """
-        ret = (-1, -1, False)
+        offset = -1
+        length = -1
+        is_last = False
+
+        next_offset = IMAGE_SIZE - ERASE_ALIGN_SIZE # Don't create padding inside the bootloader scratch page
         for i in range(0, len(self._sections)):
             s = self._sections[i]
             if s.magic == FILE_MAGIC and s.filename == filename:
                 is_last = (i == len(self._sections) - 1)
-                ret = (s.offset, s.length, is_last)
+                offset = s.offset
+                length = s.length
                 break
-        debug('%s offset %d length %d last %s' % (filename, ret[0], ret[1], ret[2]))
+
+        # Find the start of the next non padding section
+        i += 1
+        while i < len(self._sections):
+            if self._sections[i].magic == PAD_MAGIC:
+                i += 1
+            else:
+                next_offset = self._sections[i].offset
+                break
+        ret = (offset, length, is_last, next_offset)
+        debug('%s offset %d length %d is-last %d next %d' % (filename, ret[0], ret[1], ret[2], ret[3]))
         return ret
 
     def update(self, src_bytes, dst_filename):
         """
         Replaces a modifiable file with specified byte array.
         """
-        hdr_offset, length, is_last = self.find_file(dst_filename)
+        hdr_offset, length, is_last, next_offset = self.find_file(dst_filename)
+        update_len = len(src_bytes) + FILE_HDR_LEN
+
+        if hdr_offset + update_len > IMAGE_SIZE - ERASE_ALIGN_SIZE:
+            raise Exception('No space available - image past EOF.')
+
         if hdr_offset < 0:
             raise Exception('Update target %s not found' % dst_filename)
 
-        if hdr_offset + len(src_bytes) + FILE_HDR_LEN > IMAGE_SIZE:
-            raise Exception('EEPROM image size exceeded')
+        if hdr_offset + update_len > next_offset:
+            raise Exception('Update %d bytes is larger than section size %d' % (update_len, next_offset - hdr_offset))
 
         new_len = len(src_bytes) + FILENAME_LEN + 4
         struct.pack_into('>L', self._bytes, hdr_offset + 4, new_len)
@@ -312,7 +334,7 @@ class BootloaderImage(object):
         # by convention bootconf.txt is the last section and there's no need to
         # pad to the end of the sector. This also ensures that the loopback
         # config read/write tests produce identical binaries.
-        pad_bytes = ALIGN_SIZE - (pad_start % ALIGN_SIZE)
+        pad_bytes = next_offset - pad_start
         if pad_bytes > 8 and not is_last:
             pad_bytes -= 8
             struct.pack_into('>i', self._bytes, pad_start, PAD_MAGIC)
@@ -358,7 +380,7 @@ class BootloaderImage(object):
                 sys.stdout.write(self._bytes)
 
     def get_file(self, filename):
-        hdr_offset, length, is_last = self.find_file(filename)
+        hdr_offset, length, is_last, next_offset = self.find_file(filename)
         offset = hdr_offset + 4 + FILE_HDR_LEN
         file_bytes = self._bytes[offset:offset+length-FILENAME_LEN-4]
         return file_bytes
diff --git a/test/bootconf-2024.txt b/test/bootconf-2024.txt
deleted file mode 100644
index 77db039..0000000
--- a/test/bootconf-2024.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-[all]
-BOOT_UART=0
-WAKE_ON_GPIO=1
-POWER_OFF_ON_HALT=0
-[none]                                                                              
-userdata0=0x12345789
-userdata1=0x12345789
-userdata2=0x12345789
-userdata3=0x12345789
-userdata4=0x12345789
-userdata5=0x12345789
-userdata6=0x12345789
-userdata7=0x12345789
-userdata8=0x12345789
-userdata9=0x12345789
-usercert=ZZZZZZZZZZZZlhEAAAADAQABAAABAQDg2l41l7troIKOA0hk3p9y4KuITWBL/aaTMORoqmXfyqEONNULSMElaLWch/b8ScHmcS+kxkS5DtLmKFo1JI14IaQNL5fr4C6Dp23CyMGIgjp3ZFg9tXs/qWpw36Ge0MCxjabbFeKVcMXD10voMT0AHfJtQb2YfOl37ffzC4bR3phUnp0Ceqpl0Loe6hxUP/r4Jen1OKskdfjsldfjalAjn9ASdkjnkjbaAKjnLKJbaKJHDRDkllDAlciaIKSPX2b0uk2MJRJhfarMHDnmxZtEzqMgwLdLol9XVjiSu/7EUzR9Qtvs8xhf6XuUJPRD6OtJCb49L+bb/pXAej/GOk0f
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# ++++++++++++++++++++++++++++++++++++++++++++++++
diff --git a/test/bootconf-2025.txt b/test/bootconf-2025.txt
deleted file mode 100644
index e7752e4..0000000
--- a/test/bootconf-2025.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-[all]
-BOOT_UART=0
-WAKE_ON_GPIO=1
-POWER_OFF_ON_HALT=0
-[none]                                                                              
-userdata0=0x12345789
-userdata1=0x12345789
-userdata2=0x12345789
-userdata3=0x12345789
-userdata4=0x12345789
-userdata5=0x12345789
-userdata6=0x12345789
-userdata7=0x12345789
-userdata8=0x12345789
-userdata9=0x12345789
-usercert=ZZZZZZZZZZZZlhEAAAADAQABAAABAQDg2l41l7troIKOA0hk3p9y4KuITWBL/aaTMORoqmXfyqEONNULSMElaLWch/b8ScHmcS+kxkS5DtLmKFo1JI14IaQNL5fr4C6Dp23CyMGIgjp3ZFg9tXs/qWpw36Ge0MCxjabbFeKVcMXD10voMT0AHfJtQb2YfOl37ffzC4bR3phUnp0Ceqpl0Loe6hxUP/r4Jen1OKskdfjsldfjalAjn9ASdkjnkjbaAKjnLKJbaKJHDRDkllDAlciaIKSPX2b0uk2MJRJhfarMHDnmxZtEzqMgwLdLol9XVjiSu/7EUzR9Qtvs8xhf6XuUJPRD6OtJCb49L+bb/pXAej/GOk0f
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
-# ++++++++++++++++++++++++++++++++++++++++++++++++!
diff --git a/test/bootconf-4076.txt b/test/bootconf-4076.txt
new file mode 100644
index 0000000..a455332
--- /dev/null
+++ b/test/bootconf-4076.txt
@@ -0,0 +1,46 @@
+[all]
+BOOT_UART=0
+WAKE_ON_GPIO=1
+POWER_OFF_ON_HALT=0
+[none]                                                                              
+userdata0=0x12345789
+userdata1=0x12345789
+userdata2=0x12345789
+userdata3=0x12345789
+userdata4=0x12345789
+userdata5=0x12345789
+userdata6=0x12345789
+userdata7=0x12345789
+userdata8=0x12345789
+userdata9=0x12345789
+usercert=ZZZZZZZZZZZZlhEAAAADAQABAAABAQDg2l41l7troIKOA0hk3p9y4KuITWBL/aaTMORoqmXfyqEONNULSMElaLWch/b8ScHmcS+kxkS5DtLmKFo1JI14IaQNL5fr4C6Dp23CyMGIgjp3ZFg9tXs/qWpw36Ge0MCxjabbFeKVcMXD10voMT0AHfJtQb2YfOl37ffzC4bR3phUnp0Ceqpl0Loe6hxUP/r4Jen1OKskdfjsldfjalAjn9ASdkjnkjbaAKjnLKJbaKJHDRDkllDAlciaIKSPX2b0uk2MJRJhfarMHDnmxZtEzqMgwLdLol9XVjiSu/7EUzR9Qtvs8xhf6XuUJPRD6OtJCb49L+bb/pXAej/GOk0f
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
diff --git a/test/bootconf-4077.txt b/test/bootconf-4077.txt
new file mode 100644
index 0000000..1f8c3dc
--- /dev/null
+++ b/test/bootconf-4077.txt
@@ -0,0 +1,46 @@
+[all]
+BOOT_UART=0
+WAKE_ON_GPIO=1
+POWER_OFF_ON_HALT=0
+[none]                                                                              
+userdata0=0x12345789
+userdata1=0x12345789
+userdata2=0x12345789
+userdata3=0x12345789
+userdata4=0x12345789
+userdata5=0x12345789
+userdata6=0x12345789
+userdata7=0x12345789
+userdata8=0x12345789
+userdata9=0x12345789
+usercert=ZZZZZZZZZZZZlhEAAAADAQABAAABAQDg2l41l7troIKOA0hk3p9y4KuITWBL/aaTMORoqmXfyqEONNULSMElaLWch/b8ScHmcS+kxkS5DtLmKFo1JI14IaQNL5fr4C6Dp23CyMGIgjp3ZFg9tXs/qWpw36Ge0MCxjabbFeKVcMXD10voMT0AHfJtQb2YfOl37ffzC4bR3phUnp0Ceqpl0Loe6hxUP/r4Jen1OKskdfjsldfjalAjn9ASdkjnkjbaAKjnLKJbaKJHDRDkllDAlciaIKSPX2b0uk2MJRJhfarMHDnmxZtEzqMgwLdLol9XVjiSu/7EUzR9Qtvs8xhf6XuUJPRD6OtJCb49L+bb/pXAej/GOk0f
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 
+# +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
diff --git a/test/test-rpi-eeprom-config b/test/test-rpi-eeprom-config
index 25acdd7..baec697 100755
--- a/test/test-rpi-eeprom-config
+++ b/test/test-rpi-eeprom-config
@@ -135,7 +135,7 @@ check_conf_size_large()
 {
    echo "check maximum config file size"
    image="${script_dir}/$1"
-   conf="bootconf-2024.txt"
+   conf="bootconf-4076.txt"
 
    expected_md5="$(md5sum "${conf}" | awk '{print $1}')"
 
@@ -154,7 +154,7 @@ check_conf_size_too_large()
 {
    echo "check config file which exceeds the maximum size"
    image="${script_dir}/$1"
-   conf="bootconf-2025.txt"
+   conf="bootconf-4077.txt"
 
    expected_md5="$(md5sum "${conf}" | awk '{print $1}')"