diff --git a/Makefile b/Makefile
index 21aa08c..b8c60da 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 .PHONY: test
 test: vet
-	go test -v -count 1 ./...
+	go tool gotest -v -count 1 ./...
 
 .PHONY: vet
 vet:
diff --git a/db.go b/db.go
index d84d3af..9371c92 100644
--- a/db.go
+++ b/db.go
@@ -60,6 +60,7 @@ import (
 	"fmt"
 	"io"
 	"sync"
+	"sync/atomic"
 
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/stdlib"
@@ -106,12 +107,14 @@ func register0(name, drv, dsn string, readOnly bool) {
 // when the Close is called, transaction is rolled back
 type conn struct {
 	sync.Mutex
-	tx         *sql.Tx
-	dsn        string
-	opened     int
-	drv        *txDriver
-	savepoints []int
-	log        io.Writer
+	tx              *sql.Tx
+	dsn             string
+	opened          int
+	drv             *txDriver
+	savepoints      []int
+	log             io.Writer
+	readOnly        bool
+	readOnlyApplied atomic.Bool
 }
 
 type txDriver struct {
@@ -166,12 +169,6 @@ func (d *txDriver) Open(dsn string) (driver.Conn, error) {
 				return nil, err
 			}
 			opts := []stdlib.OptionOpenDB{}
-			if d.readOnly {
-				opts = append(opts, stdlib.OptionAfterConnect(func(ctx context.Context, c *pgx.Conn) error {
-					_, err := c.Exec(ctx, "SET default_transaction_read_only = true")
-					return err
-				}))
-			}
 			connector := stdlib.GetConnector(*cc, opts...)
 			d.db = sql.OpenDB(connector)
 		} else {
@@ -185,7 +182,7 @@ func (d *txDriver) Open(dsn string) (driver.Conn, error) {
 	}
 	c, ok := d.conns[dsn]
 	if !ok {
-		c = &conn{dsn: dsn, drv: d, savepoints: []int{0}, log: d.log}
+		c = &conn{dsn: dsn, drv: d, savepoints: []int{0}, log: d.log, readOnly: d.readOnly}
 		fmt.Fprintf(c.log, "%s: open\n", c.dsn)
 		c.tx, err = d.db.Begin()
 		d.conns[dsn] = c
@@ -194,6 +191,17 @@ func (d *txDriver) Open(dsn string) (driver.Conn, error) {
 	return c, err
 }
 
+func (c *conn) setReadOnlyIfNeed() error {
+	if !c.readOnly || c.readOnlyApplied.Load() {
+		return nil
+	}
+	if _, err := c.tx.Exec("SET transaction_read_only = true"); err != nil {
+		return fmt.Errorf("failed to set transaction_read_only: %w", err)
+	}
+	c.readOnlyApplied.Store(true)
+	return nil
+}
+
 func (c *conn) Close() (err error) {
 	c.drv.Lock()
 	defer c.drv.Unlock()
@@ -255,6 +263,9 @@ func (c *conn) Exec(query string, args []driver.Value) (driver.Result, error) {
 	defer c.Unlock()
 
 	fmt.Fprintf(c.log, "%s: exec %s\n", c.dsn, query)
+	if err := c.setReadOnlyIfNeed(); err != nil {
+		return nil, err
+	}
 	return c.tx.Exec(query, mapArgs(args)...)
 }
 
@@ -270,6 +281,10 @@ func (c *conn) Query(query string, args []driver.Value) (driver.Rows, error) {
 	c.Lock()
 	defer c.Unlock()
 
+	if err := c.setReadOnlyIfNeed(); err != nil {
+		return nil, err
+	}
+
 	// query rows
 	rs, err := c.tx.Query(query, mapArgs(args)...)
 	if err != nil {
@@ -412,6 +427,10 @@ func (c *conn) QueryContext(ctx context.Context, query string, args []driver.Nam
 	c.Lock()
 	defer c.Unlock()
 
+	if err := c.setReadOnlyIfNeed(); err != nil {
+		return nil, err
+	}
+
 	rs, err := c.tx.QueryContext(ctx, query, mapNamedArgs(args)...)
 	if err != nil {
 		return nil, err
@@ -427,6 +446,9 @@ func (c *conn) ExecContext(ctx context.Context, query string, args []driver.Name
 	defer c.Unlock()
 
 	fmt.Fprintf(c.log, "%s: exec %s\n", c.dsn, query)
+	if err := c.setReadOnlyIfNeed(); err != nil {
+		return nil, err
+	}
 	return c.tx.ExecContext(ctx, query, mapNamedArgs(args)...)
 }
 
diff --git a/go.mod b/go.mod
index 5826cac..cd26362 100644
--- a/go.mod
+++ b/go.mod
@@ -8,9 +8,16 @@ require (
 )
 
 require (
+	github.com/fatih/color v1.18.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	github.com/mattn/go-colorable v0.1.14 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/rakyll/gotest v0.0.7 // indirect
 	golang.org/x/sync v0.18.0 // indirect
+	golang.org/x/sys v0.40.0 // indirect
 	golang.org/x/text v0.31.0 // indirect
 )
+
+tool github.com/rakyll/gotest
diff --git a/go.sum b/go.sum
index ee8ea8a..1c03c41 100644
--- a/go.sum
+++ b/go.sum
@@ -1,6 +1,8 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fatih/color v1.18.0 h1:S8gINlzdQ840/4pfAwic/ZE0djQEH3wM94VfqLTZcOM=
+github.com/fatih/color v1.18.0/go.mod h1:4FelSpRwEGDpQ12mAdzqdOukCy4u8WUtOY6lkT/6HfU=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
@@ -9,10 +11,16 @@ github.com/jackc/pgx/v5 v5.8.0 h1:TYPDoleBBme0xGSAX3/+NujXXtpZn9HBONkQC7IEZSo=
 github.com/jackc/pgx/v5 v5.8.0/go.mod h1:QVeDInX2m9VyzvNeiCJVjCkNFqzsNb43204HshNSZKw=
 github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
 github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
+github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
+github.com/mattn/go-colorable v0.1.14/go.mod h1:6LmQG8QLFO4G5z1gPvYEzlUgJ2wF+stgPZH1UqBm1s8=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rakyll/gotest v0.0.7 h1:CL4D+fVEL0cUS5ys1cjrd+pN7sb8s1uf2LUy3UqyhAo=
+github.com/rakyll/gotest v0.0.7/go.mod h1:F/7ufCiqpm6I79Epl+SQ7tc03zSdgcf7yZsGyBH60+Q=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
@@ -20,6 +28,9 @@ github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 golang.org/x/sync v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
 golang.org/x/sync v0.18.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
+golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
 golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=