diff --git a/README.rst b/README.rst
index 0178c62..2c2fa2e 100644
--- a/README.rst
+++ b/README.rst
@@ -38,6 +38,8 @@ or individual libraries can be installed using
 
 `Purchase one from the Adafruit shop <http://www.adafruit.com/products/5974>`_
 
+This driver does not support MCU's without longint support.
+
 Installing from PyPI
 =====================
 
diff --git a/adafruit_hx711/hx711.py b/adafruit_hx711/hx711.py
index e1503b4..584f987 100644
--- a/adafruit_hx711/hx711.py
+++ b/adafruit_hx711/hx711.py
@@ -123,7 +123,7 @@ def _read_channel_raw(self, chan_gain: int) -> int:
 
         # Convert to 32-bit signed integer
         if value & 0x80_00_00:
-            value -= 0x1_00_00_00
+            value |= 0xFF_00_00_00
 
         return value