diff --git a/Processor.cs b/Processor.cs
index 189c745..e6d23b4 100644
--- a/Processor.cs
+++ b/Processor.cs
@@ -454,7 +454,7 @@ public bool Execute(bool runUntilHalt, Stream? stdoutOverride = null)
 
                                 Registers[(int)Register.rsf] &= ~(ulong)StatusFlags.Overflow;
 
-                                if (result < initial)
+                                if (result < initial && mathend != 0)
                                 {
                                     Registers[(int)Register.rsf] |= (ulong)StatusFlags.Carry;
                                 }