diff --git a/src/llvm_abi.cpp b/src/llvm_abi.cpp
index 4d67af46e..2e1e505f2 100644
--- a/src/llvm_abi.cpp
+++ b/src/llvm_abi.cpp
@@ -486,6 +486,7 @@ namespace lbAbiAmd64Win64 {
 		switch (calling_convention) {
 		case ProcCC_Odin:
 		case ProcCC_Contextless:
+			return true;
 		case ProcCC_VectorCall:
 			return true;
 		}
@@ -501,12 +502,27 @@ namespace lbAbiAmd64Win64 {
 
 			if (is_vectorcall(calling_convention)) {
 				if (kind == LLVMStructTypeKind || kind == LLVMArrayTypeKind) {
+				#if 0
 					i64 sz = lb_sizeof(t);
 					if (sz <= 8) {
 						args[i] = lb_arg_type_direct(t, LLVMIntTypeInContext(c, 8*cast(unsigned)sz), nullptr, nullptr);
 					} else {
 						args[i] = lb_arg_type_indirect(t, nullptr);
 					}
+				#else
+					i64 sz = lb_sizeof(t);
+					switch (sz) {
+					case 1:
+					case 2:
+					case 4:
+					case 8:
+						args[i] = lb_arg_type_direct(t, LLVMIntTypeInContext(c, 8*cast(unsigned)sz), nullptr, nullptr);
+						break;
+					default:
+						args[i] = lb_arg_type_indirect(t, nullptr);
+						break;
+					}
+				#endif
 				}
 
 				if (kind == LLVMVectorTypeKind) {
diff --git a/src/llvm_backend.hpp b/src/llvm_backend.hpp
index e4297300f..7bd9da036 100644
--- a/src/llvm_backend.hpp
+++ b/src/llvm_backend.hpp
@@ -741,6 +741,7 @@ lbCallingConventionKind const lb_calling_convention_map[ProcCC_MAX] = {
 	lbCallingConvention_PreserveMost,  // ProcCC_PreserveMost,
 	lbCallingConvention_PreserveAll,   // ProcCC_PreserveAll,
 
+	lbCallingConvention_X86_VectorCall, // ProcCC_VectorCall,
 };
 
 enum : LLVMDWARFTypeEncoding {
diff --git a/src/parser.hpp b/src/parser.hpp
index e712c136a..8955608de 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -305,7 +305,7 @@ enum ProcCallingConvention : i32 {
 	ProcCC_PreserveMost = 12,
 	ProcCC_PreserveAll  = 13,
 
-	ProcCC_VectorCall  = 14,
+	ProcCC_VectorCall   = 14,
 
 	ProcCC_MAX,