diff --git a/cpu.cpp b/cpu.cpp
index a445341..e3876de 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -796,19 +796,14 @@ bool cpu::additional_double_operand_instructions(const uint16_t instr)
 			}
 
 		case 7: { // SOB
-				uint16_t v = getRegister(reg);
-
-				if (v == 1)
-					v = 0;
-				else {
-					v--;
+				addRegister(reg, rm_cur, -1);
 
+				if (getRegister(reg)) {
 					uint16_t newPC = getPC() - dst * 2;
+
 					setPC(newPC);
 				}
 
-				setRegister(reg, v);
-
 				return true;
 			}
 	}