diff --git a/src/backend_x64/block_of_code.cpp b/src/backend_x64/block_of_code.cpp
index 73a381b7..53dc448e 100644
--- a/src/backend_x64/block_of_code.cpp
+++ b/src/backend_x64/block_of_code.cpp
@@ -18,6 +18,20 @@
 namespace Dynarmic {
 namespace BackendX64 {
 
+#ifdef _WIN32
+const Xbyak::Reg64 BlockOfCode::ABI_RETURN = Xbyak::util::rax;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM1 = Xbyak::util::rcx;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM2 = Xbyak::util::rdx;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM3 = Xbyak::util::r8;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM4 = Xbyak::util::r9;
+#else
+const Xbyak::Reg64 BlockOfCode::ABI_RETURN = Xbyak::util::rax;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM1 = Xbyak::util::rdi;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM2 = Xbyak::util::rsi;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM3 = Xbyak::util::rdx;
+const Xbyak::Reg64 BlockOfCode::ABI_PARAM4 = Xbyak::util::rcx;
+#endif
+
 constexpr size_t TOTAL_CODE_SIZE = 128 * 1024 * 1024;
 constexpr size_t FAR_CODE_OFFSET = 100 * 1024 * 1024;
 
diff --git a/src/backend_x64/block_of_code.h b/src/backend_x64/block_of_code.h
index f0b16f64..3a986bb7 100644
--- a/src/backend_x64/block_of_code.h
+++ b/src/backend_x64/block_of_code.h
@@ -112,19 +112,11 @@ public:
     void SetCodePtr(CodePtr code_ptr);
     void EnsurePatchLocationSize(CodePtr begin, size_t size);
 
-#ifdef _WIN32
-    Xbyak::Reg64 ABI_RETURN = rax;
-    Xbyak::Reg64 ABI_PARAM1 = rcx;
-    Xbyak::Reg64 ABI_PARAM2 = rdx;
-    Xbyak::Reg64 ABI_PARAM3 = r8;
-    Xbyak::Reg64 ABI_PARAM4 = r9;
-#else
-    Xbyak::Reg64 ABI_RETURN = rax;
-    Xbyak::Reg64 ABI_PARAM1 = rdi;
-    Xbyak::Reg64 ABI_PARAM2 = rsi;
-    Xbyak::Reg64 ABI_PARAM3 = rdx;
-    Xbyak::Reg64 ABI_PARAM4 = rcx;
-#endif
+    static const Xbyak::Reg64 ABI_RETURN;
+    static const Xbyak::Reg64 ABI_PARAM1;
+    static const Xbyak::Reg64 ABI_PARAM2;
+    static const Xbyak::Reg64 ABI_PARAM3;
+    static const Xbyak::Reg64 ABI_PARAM4;
 
 private:
     UserCallbacks cb;