diff --git a/cl/_testrt/mask/in.go b/cl/_testrt/mask/in.go
new file mode 100644
index 00000000..18211c06
--- /dev/null
+++ b/cl/_testrt/mask/in.go
@@ -0,0 +1,8 @@
+package main
+
+func main() {
+	println(mask(1))
+}
+func mask(x int8) int32 {
+	return int32(x) << 31 >> 31
+}
diff --git a/cl/_testrt/mask/out.ll b/cl/_testrt/mask/out.ll
new file mode 100644
index 00000000..bea4f657
--- /dev/null
+++ b/cl/_testrt/mask/out.ll
@@ -0,0 +1,52 @@
+; ModuleID = 'main'
+source_filename = "main"
+
+%"github.com/goplus/llgo/internal/runtime.String" = type { ptr, i64 }
+
+@"main.init$guard" = global ptr null
+@__llgo_argc = global ptr null
+@__llgo_argv = global ptr null
+@0 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+
+define void @main.init() {
+_llgo_0:
+  %0 = load i1, ptr @"main.init$guard", align 1
+  br i1 %0, label %_llgo_2, label %_llgo_1
+
+_llgo_1:                                          ; preds = %_llgo_0
+  store i1 true, ptr @"main.init$guard", align 1
+  br label %_llgo_2
+
+_llgo_2:                                          ; preds = %_llgo_1, %_llgo_0
+  ret void
+}
+
+define void @main(i32 %0, ptr %1) {
+_llgo_0:
+  store i32 %0, ptr @__llgo_argc, align 4
+  store ptr %1, ptr @__llgo_argv, align 8
+  call void @"github.com/goplus/llgo/internal/runtime.init"()
+  call void @main.init()
+  %2 = call i32 @main.mask(i8 1)
+  %3 = sext i32 %2 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %3)
+  %4 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @0, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %4)
+  ret void
+}
+
+define i32 @main.mask(i8 %0) {
+_llgo_0:
+  %1 = sext i8 %0 to i32
+  %2 = shl i32 %1, 31
+  %3 = ashr i32 %2, 31
+  ret i32 %3
+}
+
+declare void @"github.com/goplus/llgo/internal/runtime.init"()
+
+declare void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64)
+
+declare void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String")
+
+declare %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr, i64)
diff --git a/ssa/expr.go b/ssa/expr.go
index 89d70c55..7dfa45a0 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -328,6 +328,11 @@ func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 		if op == token.SHR && kind == vkUnsigned {
 			llop = llvm.LShr // Logical Shift Right
 		}
+		if op == token.SHL || op == token.SHR {
+			if b.Prog.SizeOf(x.Type) != b.Prog.SizeOf(y.Type) {
+				y = b.Convert(x.Type, y)
+			}
+		}
 		return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 	case isPredOp(op): // op: == != < <= < >=
 		tret := b.Prog.Bool()