diff --git a/cpu/decoder.cpp b/cpu/decoder.cpp
index a34dcdd..640e714 100644
--- a/cpu/decoder.cpp
+++ b/cpu/decoder.cpp
@@ -172,6 +172,16 @@ void Cpu::executeInstruction()
           mcycles = 3;
         }
     }
+  else if((op & 0xCF) == 0x09) // ADD HL, rr
+    {
+      u16 rhs = state.reg16((op >> 4) & 0x3);
+      u16 res12 = (state.HL & 0x0FFF) + (rhs & 0x0FFF);
+      state.halfcarry = (res11 & 0x1000);
+      u32 res32 = (u32)state.HL + (u32)rhs;
+      state.carry = (res32 & 0x10000);
+      state.subtract = false;
+      mcycles = 2;
+    }
   else if((op & 0xE7) == 0xC0) // RET cc
     {
       if(decodeCond((op >> 3) & 0x3))
diff --git a/types.h b/types.h
index 0ed4a10..3489fe5 100644
--- a/types.h
+++ b/types.h
@@ -2,6 +2,8 @@
 
 typedef unsigned char u8;
 typedef unsigned short u16;
+typedef unsigned int u32;
 
 typedef signed char s8;
 typedef signed short s16;
+typedef signed int s32;