diff --git a/internal/pwru/output.go b/internal/pwru/output.go
index f172e357..a61035ad 100644
--- a/internal/pwru/output.go
+++ b/internal/pwru/output.go
@@ -7,7 +7,6 @@ package pwru
 import (
 	"errors"
 	"fmt"
-	"io"
 	"log"
 	"net"
 	"os"
@@ -36,7 +35,7 @@ type output struct {
 	printSkbMap   *ebpf.Map
 	printStackMap *ebpf.Map
 	addr2name     Addr2Name
-	writer        io.Writer
+	writer        *os.File
 	kprobeMulti   bool
 	kfreeReasons  map[uint64]string
 	ifaceCache    map[uint64]map[uint32]string
@@ -81,6 +80,13 @@ func NewOutput(flags *Flags, printSkbMap *ebpf.Map, printStackMap *ebpf.Map,
 	}, nil
 }
 
+func (o *output) Close() {
+	if o.writer != os.Stdout {
+		_ = o.writer.Sync()
+		_ = o.writer.Close()
+	}
+}
+
 func (o *output) PrintHeader() {
 	if o.flags.OutputTS == "absolute" {
 		fmt.Fprintf(o.writer, "%12s ", "TIME")
diff --git a/main.go b/main.go
index aa981b09..aff0021f 100644
--- a/main.go
+++ b/main.go
@@ -315,6 +315,7 @@ func main() {
 	if err != nil {
 		log.Fatalf("Failed to create outputer: %s", err)
 	}
+	defer output.Close()
 	output.PrintHeader()
 
 	defer func() {