diff --git a/cl/_testrt/structsize/in.go b/cl/_testrt/structsize/in.go
new file mode 100644
index 00000000..0e83f67c
--- /dev/null
+++ b/cl/_testrt/structsize/in.go
@@ -0,0 +1,19 @@
+package main
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+type Foo struct {
+	A byte
+	B uint8
+	C uint16
+	D byte
+	E [8]int8
+}
+
+func main() {
+	c.Printf(c.Str("%d"), unsafe.Sizeof(Foo{}))
+}
diff --git a/cl/_testrt/structsize/out.ll b/cl/_testrt/structsize/out.ll
new file mode 100644
index 00000000..643a449e
--- /dev/null
+++ b/cl/_testrt/structsize/out.ll
@@ -0,0 +1,34 @@
+; ModuleID = 'main'
+source_filename = "main"
+
+@"main.init$guard" = global i1 false, align 1
+@__llgo_argc = global i32 0, align 4
+@__llgo_argv = global ptr null, align 8
+@0 = private unnamed_addr constant [3 x i8] c"%d\00", align 1
+
+define void @main.init() {
+_llgo_0:
+  %0 = load i1, ptr @"main.init$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 i32 @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 (ptr, ...) @printf(ptr @0, i64 14)
+  ret i32 0
+}
+
+declare void @"github.com/goplus/llgo/internal/runtime.init"()
+
+declare i32 @printf(ptr, ...)
diff --git a/ssa/type.go b/ssa/type.go
index 3b6e85f9..af48f47c 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -114,7 +114,11 @@ func (p *goProgram) Offsetsof(fields []*types.Var) (ret []int64) {
 func (p *goProgram) Sizeof(T types.Type) int64 {
 	prog := Program(p)
 	ptrSize := int64(prog.PointerSize())
-	return prog.sizes.Sizeof(T) + extraSize(T, ptrSize)
+	baseSize := prog.sizes.Sizeof(T) + extraSize(T, ptrSize)
+	if _, ok := T.Underlying().(*types.Struct); ok {
+		return align(baseSize, prog.sizes.Alignof(T))
+	}
+	return baseSize
 }
 
 func extraSize(t types.Type, ptrSize int64) (ret int64) {
@@ -134,6 +138,10 @@ func extraSize(t types.Type, ptrSize int64) (ret int64) {
 	return 0
 }
 
+func align(x, a int64) int64 {
+	return (x + a - 1) &^ (a - 1)
+}
+
 // -----------------------------------------------------------------------------
 
 type rawType struct {