diff --git a/cl/_testrt/callback/in.go b/cl/_testrt/callback/in.go
index 3e2466f5..833bb900 100644
--- a/cl/_testrt/callback/in.go
+++ b/cl/_testrt/callback/in.go
@@ -4,12 +4,15 @@ import (
 	"github.com/goplus/llgo/internal/runtime/c"
 )
 
-func callback(f func()) {
-	f()
+func callback(msg *c.Char, f func(*c.Char)) {
+	f(msg)
+}
+
+func print(msg *c.Char) {
+	c.Printf(msg)
 }
 
 func main() {
-	callback(func() {
-		c.Printf(c.Str("Hello, callback\n"))
-	})
+	callback(c.Str("Hello\n"), print)
+	callback(c.Str("callback\n"), print)
 }
diff --git a/cl/_testrt/callback/out.ll b/cl/_testrt/callback/out.ll
index af9f93d3..6156c095 100644
--- a/cl/_testrt/callback/out.ll
+++ b/cl/_testrt/callback/out.ll
@@ -2,12 +2,14 @@
 source_filename = "main"
 
 @"main.init$guard" = global ptr null
-@0 = private unnamed_addr constant [17 x i8] c"Hello, callback\0A\00", align 1
+@0 = private unnamed_addr constant [7 x i8] c"Hello\0A\00", align 1
+@1 = private unnamed_addr constant [10 x i8] c"callback\0A\00", align 1
 
-define void @main.callback({ ptr, ptr } %0) {
+define void @main.callback(ptr %0, { ptr, ptr } %1) {
 _llgo_0:
-  %1 = extractvalue { ptr, ptr } %0, 0
-  call void %1()
+  %2 = extractvalue { ptr, ptr } %1, 1
+  %3 = extractvalue { ptr, ptr } %1, 0
+  call void %3(ptr %2, ptr %0)
   ret void
 }
 
@@ -30,19 +32,40 @@ _llgo_0:
   call void @main.init()
   %0 = alloca { ptr, ptr }, align 8
   %1 = getelementptr inbounds { ptr, ptr }, ptr %0, i32 0, i32 0
-  store ptr @"main.main$1", ptr %1, align 8
+  store ptr @__llgo_stub.main.print, ptr %1, align 8
   %2 = getelementptr inbounds { ptr, ptr }, ptr %0, i32 0, i32 1
   store ptr null, ptr %2, align 8
   %3 = load { ptr, ptr }, ptr %0, align 8
-  call void @main.callback({ ptr, ptr } %3)
+  call void @main.callback(ptr @0, { ptr, ptr } %3)
+  %4 = alloca { ptr, ptr }, align 8
+  %5 = getelementptr inbounds { ptr, ptr }, ptr %4, i32 0, i32 0
+  store ptr @__llgo_stub.main.print, ptr %5, align 8
+  %6 = getelementptr inbounds { ptr, ptr }, ptr %4, i32 0, i32 1
+  store ptr null, ptr %6, align 8
+  %7 = load { ptr, ptr }, ptr %4, align 8
+  call void @main.callback(ptr @1, { ptr, ptr } %7)
   ret void
 }
 
+define void @main.print(ptr %0) {
+_llgo_0:
+  %1 = call i32 (ptr, ...) @printf(ptr %0)
+  ret void
+  %2 = call i32 (ptr, ...) @printf(ptr %0)
+  ret void
+  %3 = call i32 (ptr, ...) @printf(ptr %0)
+  ret void
+
+_llgo_01:                                         ; No predecessors!
+
+_llgo_02:                                         ; No predecessors!
+}
+
 declare void @"github.com/goplus/llgo/internal/runtime.init"()
 
-define void @"main.main$1"() {
+define void @__llgo_stub.main.print(ptr %0, ptr %1) {
 _llgo_0:
-  %0 = call i32 (ptr, ...) @printf(ptr @0)
+  call void @main.print(ptr %1)
   ret void
 }
 
diff --git a/internal/llgen/llgen.go b/internal/llgen/llgen.go
index d56b809e..fafcb959 100644
--- a/internal/llgen/llgen.go
+++ b/internal/llgen/llgen.go
@@ -71,6 +71,11 @@ func Gen(pkgPath, inFile string, src any) string {
 	}
 
 	prog := llssa.NewProgram(nil)
+	prog.SetRuntime(func() *types.Package {
+		rt, err := imp.Import(llssa.PkgRuntime)
+		check(err)
+		return rt
+	})
 	ret, err := cl.NewPackage(prog, ssaPkg, files)
 	check(err)
 
diff --git a/ssa/package.go b/ssa/package.go
index a0de6d0b..e58cff70 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -377,6 +377,7 @@ func (p Package) closureStub(b Builder, t *types.Struct, v Expr) Expr {
 	} else {
 		sig := v.raw.Type.(*types.Signature)
 		n := sig.Params().Len()
+		nret := sig.Results().Len()
 		ctx := types.NewParam(token.NoPos, nil, ClosureCtx, types.Typ[types.UnsafePointer])
 		sig = FuncAddCtx(ctx, sig)
 		fn := p.NewFunc(ClosureStub+name, sig, InC)
@@ -385,7 +386,13 @@ func (p Package) closureStub(b Builder, t *types.Struct, v Expr) Expr {
 			args[i] = fn.Param(i + 1)
 		}
 		b := fn.MakeBody(1)
-		b.Return(b.Call(v, args...))
+		call := b.Call(v, args...)
+		switch nret {
+		case 0:
+			b.impl.CreateRetVoid()
+		default: // TODO(xsw): support multiple return values
+			b.impl.CreateRet(call.impl)
+		}
 		p.stubs[name] = fn
 		v = fn.Expr
 	}