diff --git a/cpu/decoder.cpp b/cpu/decoder.cpp
index f945d32..989e199 100644
--- a/cpu/decoder.cpp
+++ b/cpu/decoder.cpp
@@ -119,14 +119,9 @@ void Cpu::executeInstruction()
           break;
         }
     }
-  else if((op & 0xCF) == 0x03) // INC rr
+  else if((op & 0xC7) == 0x03) // INC rr; DEC rr
     {
-      state.reg16((op >> 4) & 0x3) += 1;
-      mcycles = 2;
-    }
-  else if((op & 0xCF) == 0x0B) // DEC rr
-    {
-      state.reg16((op >> 4) & 0x3) -= 1;
+      state.reg16((op >> 4) & 0x3) += ((op & 0x08) ? -1 : 1);
       mcycles = 2;
     }
   else if((op & 0xE7) == 0xC2) // JP cc, nn: