diff --git a/src/backend_x64/a64_emit_x64.cpp b/src/backend_x64/a64_emit_x64.cpp
index ab920c98..e6b4241d 100644
--- a/src/backend_x64/a64_emit_x64.cpp
+++ b/src/backend_x64/a64_emit_x64.cpp
@@ -740,7 +740,7 @@ void A64EmitX64::EmitA64WriteMemory128(A64EmitContext& ctx, IR::Inst* inst) {
     code.CallFunction(memory_write_128);
 }
 
-void A64EmitX64::EmitExclusiveWrite(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize, Xbyak::Reg64 vaddr, size_t value_idx) {
+void A64EmitX64::EmitExclusiveWrite(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize, Xbyak::Reg64 vaddr, int value_idx) {
     Xbyak::Label end;
     Xbyak::Reg32 passed = ctx.reg_alloc.ScratchGpr().cvt32();
     Xbyak::Reg32 tmp = ctx.reg_alloc.ScratchGpr().cvt32();
diff --git a/src/backend_x64/a64_emit_x64.h b/src/backend_x64/a64_emit_x64.h
index 9ba3e5d4..26c0edad 100644
--- a/src/backend_x64/a64_emit_x64.h
+++ b/src/backend_x64/a64_emit_x64.h
@@ -57,7 +57,7 @@ protected:
 
     void EmitDirectPageTableMemoryRead(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize);
     void EmitDirectPageTableMemoryWrite(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize);
-    void EmitExclusiveWrite(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize, Xbyak::Reg64 vaddr, size_t value_idx);
+    void EmitExclusiveWrite(A64EmitContext& ctx, IR::Inst* inst, size_t bitsize, Xbyak::Reg64 vaddr, int value_idx);
 
     // Microinstruction emitters
 #define OPCODE(...)