diff --git a/.gitignore b/.gitignore
index 5e7a62f..6292408 100644
--- a/.gitignore
+++ b/.gitignore
@@ -115,3 +115,7 @@ venv.bak/
 
 # Personal dev scripts
 .scripts
+
+# Mountpoints
+mnt/
+mnt2/
diff --git a/kmk/firmware.py b/kmk/firmware.py
index 4225bfb..a905dcb 100644
--- a/kmk/firmware.py
+++ b/kmk/firmware.py
@@ -139,7 +139,14 @@ class Firmware:
         if self.is_master is not None:
             return self.is_master
 
-        return supervisor.runtime.serial_connected
+        # Working around https://github.com/adafruit/circuitpython/issues/1769
+        try:
+            self._hid_helper_inst.create_report([]).send()
+            self.is_master = True
+        except OSError:
+            self.is_master = False
+
+        return self.is_master
 
     def init_uart(self, pin, timeout=20):
         if self._master_half():
@@ -153,6 +160,8 @@ class Firmware:
         assert self.col_pins, 'no GPIO pins defined for matrix columns'
         assert self.diode_orientation is not None, 'diode orientation must be defined'
 
+        self._hid_helper_inst = self.hid_helper()
+
         # Split keyboard Init
         if self.split_flip and not self._master_half():
             self.col_pins = list(reversed(self.col_pins))
@@ -173,8 +182,6 @@ class Firmware:
             swap_indicies=getattr(self, 'swap_indicies', None),
         )
 
-        self._hid_helper_inst = self.hid_helper()
-
         # Compile string leader sequences
         for k, v in self.leader_dictionary.items():
             if not isinstance(k, tuple):
diff --git a/kmk/matrix.py b/kmk/matrix.py
index e1be0d5..754cc7b 100644
--- a/kmk/matrix.py
+++ b/kmk/matrix.py
@@ -73,8 +73,19 @@ class MatrixScanner:
             opin.value(True)
 
             for iidx, ipin in enumerate(self.inputs):
+                # cast to int to avoid
+                #
+                # >>> xyz = bytearray(3)
+                # >>> xyz[2] = True
+                # Traceback (most recent call last):
+                #   File "<stdin>", line 1, in <module>
+                # OverflowError: value would overflow a 1 byte buffer
+                #
+                # I haven't dived too far into what causes this, but it's
+                # almost certainly because bool types in Python aren't just
+                # aliases to int values, but are proper pseudo-types
+                new_val = int(ipin.value())
                 old_val = self.state[ba_idx]
-                new_val = ipin.value()
 
                 if old_val != new_val:
                     if self.translate_coords:
@@ -97,6 +108,7 @@ class MatrixScanner:
 
                     self.report[2] = new_val
                     self.state[ba_idx] = new_val
+
                     any_changed = True
                     break