diff --git a/CHANGES.txt b/CHANGES.txt
index 21bb113..db50006 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -16,6 +16,9 @@ Next Release
   - The processor status register is now initialized to 0 on reset.
     Previously, its unused bit (bit 5) was set to 1 on reset.
 
+  - Applied patch from Ed Spittles to change the CMP algorithm so that
+    it no longer fails Rob Finch's test suite.  Closes #8. 
+
 0.6 (2009-08-11)
 
   - Added monitor shortcut "a" for "assemble".
diff --git a/src/py65/devices/mpu6502.py b/src/py65/devices/mpu6502.py
index 0ec94f0..da91c62 100644
--- a/src/py65/devices/mpu6502.py
+++ b/src/py65/devices/mpu6502.py
@@ -356,8 +356,7 @@ class MPU:
       self.flags |= self.CARRY + self.ZERO
     elif register_value > tbyte:
       self.flags |= self.CARRY
-    else:
-      self.flags |= self.NEGATIVE
+    self.flags |= (self.a - tbyte) & self.NEGATIVE
 
   def opSBC(self, x):
     data = self.ByteAt(x())