diff --git a/internal/ptx/dependencies.go b/internal/ptx/dependencies.go
index 40b4f44..6675e27 100644
--- a/internal/ptx/dependencies.go
+++ b/internal/ptx/dependencies.go
@@ -1,17 +1,8 @@
 package ptx
 
 import (
-	"context"
-	"net"
-
 	"github.com/ooni/probe-cli/v3/internal/model"
 )
 
-// UnderlyingDialer is the underlying dialer used for dialing.
-type UnderlyingDialer interface {
-	// DialContext behaves like net.Dialer.DialContext.
-	DialContext(ctx context.Context, network, address string) (net.Conn, error)
-}
-
 // defaultLogger is the default silentLogger instance.
 var defaultLogger model.Logger = model.DiscardLogger
diff --git a/internal/ptx/obfs4.go b/internal/ptx/obfs4.go
index b693762..b364a86 100644
--- a/internal/ptx/obfs4.go
+++ b/internal/ptx/obfs4.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	pt "git.torproject.org/pluggable-transports/goptlib.git"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 	"gitlab.com/yawning/obfs4.git/transports/base"
 	"gitlab.com/yawning/obfs4.git/transports/obfs4"
@@ -50,7 +51,7 @@ type OBFS4Dialer struct {
 
 	// UnderlyingDialer is the optional underlying dialer to
 	// use. If not set, we will use &net.Dialer{}.
-	UnderlyingDialer UnderlyingDialer
+	UnderlyingDialer model.SimpleDialer
 }
 
 // DialContext establishes a connection with the given obfs4 proxy. The context
@@ -94,8 +95,8 @@ func (d *OBFS4Dialer) parseargs(factory base.ClientFactory) (interface{}, error)
 	return factory.ParseArgs(args)
 }
 
-// underlyingDialer returns a suitable UnderlyingDialer.
-func (d *OBFS4Dialer) underlyingDialer() UnderlyingDialer {
+// underlyingDialer returns a suitable SimpleDialer.
+func (d *OBFS4Dialer) underlyingDialer() model.SimpleDialer {
 	if d.UnderlyingDialer != nil {
 		return d.UnderlyingDialer
 	}
@@ -120,7 +121,7 @@ type obfs4CancellableDialer struct {
 	parsedargs interface{}
 
 	// ud is the underlying Dialer to use.
-	ud UnderlyingDialer
+	ud model.SimpleDialer
 }
 
 // dial performs the dial.