diff --git a/convert/convert.go b/convert/convert.go
index a83a225..8893a92 100644
--- a/convert/convert.go
+++ b/convert/convert.go
@@ -199,24 +199,22 @@ func convert(
 			return fmt.Errorf("reading CSV: %w", err)
 		}
 
-		p, err := makePrefix(record[0])
+		prefix, err := netip.ParsePrefix(record[0])
 		if err != nil {
-			return err
+			return fmt.Errorf("parsing network (%s): %w", record[0], err)
 		}
-		err = writer.Write(makeLine(p, record[1:]))
+
+		err = writer.Write(makeLine(prefix, record[1:]))
 		if err != nil {
 			return fmt.Errorf("writing CSV: %w", err)
 		}
 	}
 
 	writer.Flush()
-	return nil
-}
 
-func makePrefix(network string) (netip.Prefix, error) {
-	prefix, err := netip.ParsePrefix(network)
-	if err != nil {
-		return prefix, fmt.Errorf("parsing network (%s): %w", network, err)
+	if err := writer.Error(); err != nil {
+		return fmt.Errorf("flushing CSV: %w", err)
 	}
-	return prefix, nil
+
+	return nil
 }
diff --git a/convert/convert_test.go b/convert/convert_test.go
index b8c0522..08368c7 100644
--- a/convert/convert_test.go
+++ b/convert/convert_test.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"net/netip"
 	"os"
 	"strings"
 	"testing"
@@ -127,7 +128,7 @@ func checkLine(
 	network string,
 	expected []string,
 ) {
-	p, err := makePrefix(network)
+	p, err := netip.ParsePrefix(network)
 	if err != nil {
 		t.Fatal(err)
 	}