diff --git a/gp2040ce_bintools/pico.py b/gp2040ce_bintools/pico.py
index 6d86892..f9a2caa 100644
--- a/gp2040ce_bintools/pico.py
+++ b/gp2040ce_bintools/pico.py
@@ -32,6 +32,15 @@ PICO_COMMANDS = {
 }
 
 
+#################
+# LIBRARY ITEMS #
+#################
+
+
+class PicoAlignmentError(ValueError):
+    """Exception raised when the address provided for an operation is invalid."""
+
+
 def get_bootsel_endpoints() -> tuple[usb.core.Endpoint, usb.core.Endpoint]:
     """Retrieve the USB endpoint for purposes of interacting with a Pico in BOOTSEL mode.
 
@@ -189,6 +198,9 @@ def write(out_end: usb.core.Endpoint, in_end: usb.core.Endpoint, location: int,
         location: memory address of where to start reading from
         content: the data to write
     """
+    if (location % 256) != 0:
+        raise PicoAlignmentError("writes must start at 256 byte boundaries, please pad or align as appropriate!")
+
     # set up the data
     command_size = 8
 
diff --git a/tests/test_pico.py b/tests/test_pico.py
index caf3b54..e55dccf 100644
--- a/tests/test_pico.py
+++ b/tests/test_pico.py
@@ -5,6 +5,7 @@ import sys
 import unittest.mock as mock
 from array import array
 
+import pytest
 from decorator import decorator
 
 import gp2040ce_bintools.pico as pico
@@ -144,3 +145,36 @@ def test_write():
     ]
     end_out.write.assert_has_calls(expected_writes)
     assert end_in.read.call_count == 6
+
+
+def test_misaligned_write():
+    """Test that we can't write to a board at invalid memory addresses."""
+    end_out, end_in = mock.MagicMock(), mock.MagicMock()
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE001, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE008, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE010, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE020, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE040, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE080, b'\x00\x01\x02\x03')
+    with pytest.raises(pico.PicoAlignmentError):
+        _ = pico.write(end_out, end_in, 0x101FE0FF, b'\x00\x01\x02\x03')
+
+    _ = pico.write(end_out, end_in, 0x101FE100, b'\x00\x01\x02\x03')
+
+    expected_writes = [
+        mock.call(struct.pack('<LLBBxxLL12x', 0x431fd10b, 1, 0x1, 1, 0, 1)),
+        mock.call(struct.pack('<LLBBxxL16x', 0x431fd10b, 1, 0x6, 0, 0)),
+        mock.call(struct.pack('<LLBBxxLLL8x', 0x431fd10b, 1, 0x3, 8, 0, 0x101FE100, 4)),
+        mock.call(struct.pack('<LLBBxxL16x', 0x431fd10b, 1, 0x6, 0, 0)),
+        mock.call(struct.pack('<LLBBxxLLL8x', 0x431fd10b, 1, 0x5, 8, 4, 0x101FE100, 4)),
+        mock.call(b'\x00\x01\x02\x03'),
+        mock.call(struct.pack('<LLBBxxLL12x', 0x431fd10b, 1, 0x1, 1, 0, 0)),
+    ]
+    end_out.write.assert_has_calls(expected_writes)
+    assert end_in.read.call_count == 6