diff --git a/task_test.go b/task_test.go
index 1d8bd48..4cab4ec 100644
--- a/task_test.go
+++ b/task_test.go
@@ -11,6 +11,7 @@ import (
 	"reflect"
 	"testing"
 
+	task "github.com/concourse/oci-build-task"
 	"github.com/google/go-containerregistry/pkg/name"
 	"github.com/google/go-containerregistry/pkg/registry"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
@@ -19,7 +20,6 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
 	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
-	task "github.com/concourse/oci-build-task"
 )
 
 type TaskSuite struct {
@@ -116,7 +116,7 @@ func (s *TaskSuite) TestTarget() {
 
 func (s *TaskSuite) TestBuildkitSSH() {
 	s.req.Config.ContextDir = "testdata/buildkit-ssh"
-	s.req.Config.BuildkitSSH = "my_ssh_key=./id_rsa_test"
+	s.req.Config.BuildkitSSH = "my_ssh_key=testdata/buildkit-ssh/id_rsa_test"
 
 	_, err := s.build()
 	s.NoError(err)
diff --git a/testdata/buildkit-ssh/Dockerfile b/testdata/buildkit-ssh/Dockerfile
index 42f55e3..51f878a 100644
--- a/testdata/buildkit-ssh/Dockerfile
+++ b/testdata/buildkit-ssh/Dockerfile
@@ -1,5 +1,7 @@
 # syntax = docker/dockerfile:1.0-experimental
 FROM alpine
 
-# shows secret from custom secret location:
-RUN --mount=type=secret,id=my_ssh_key cat ./id_rsa_test
+RUN apk add --no-cache openssh-client
+
+# shows private key available in ssh agent
+RUN --mount=type=ssh,id=my_ssh_key ssh-add -l | grep "SHA256:DFxHFuit9VQtxkBrZWzJhf5OTL5/RwzCJuZjTAPC1DI"