diff --git a/cpu/decoder.cpp b/cpu/decoder.cpp
index 640e714..0a599e0 100644
--- a/cpu/decoder.cpp
+++ b/cpu/decoder.cpp
@@ -455,6 +455,18 @@ void Cpu::executeInstruction()
           state.IME = IME_SCHEDULED;
           break;
 
+        case 0xE8: // ADD SP, e8
+          u32 lhs = state.SP;
+          s32 rhs = (s8)readPC8();
+          u32 low_add = (lhs & 0x0FFF) + (rhs & 0x0FFF);
+          state.halfcarry = (low_add & 0x1000);
+          u32 res32 = lhs + rhs;
+          state.carry = (res32 & 0x10000);
+          state.SP = (u16)res32;
+          state.subtract = false;
+          state.zero = false;
+          mcycles = 4;
+
         default:
           panic("Unknown opcode 0x%x\n",op);
         }