diff --git a/internal/plugin/runtime_subprocess.go b/internal/plugin/runtime_subprocess.go
index c836c1c6d..1d47ba745 100644
--- a/internal/plugin/runtime_subprocess.go
+++ b/internal/plugin/runtime_subprocess.go
@@ -255,7 +255,7 @@ func (r *SubprocessPluginRuntime) runPostrenderer(input *Input) (*Output, error)
 
 	go func() {
 		defer stdin.Close()
-		io.Copy(stdin, msg.Manifests)
+		io.Copy(stdin, bytes.NewBufferString(msg.Manifests))
 	}()
 
 	postRendered := &bytes.Buffer{}
@@ -272,7 +272,7 @@ func (r *SubprocessPluginRuntime) runPostrenderer(input *Input) (*Output, error)
 
 	return &Output{
 		Message: schema.OutputMessagePostRendererV1{
-			Manifests: postRendered,
+			Manifests: postRendered.String(),
 		},
 	}, nil
 }
diff --git a/internal/plugin/schema/postrenderer.go b/internal/plugin/schema/postrenderer.go
index ef51a8a61..cda29b4b2 100644
--- a/internal/plugin/schema/postrenderer.go
+++ b/internal/plugin/schema/postrenderer.go
@@ -16,19 +16,15 @@ limitations under the License.
 
 package schema
 
-import (
-	"bytes"
-)
-
 // InputMessagePostRendererV1 implements Input.Message
 type InputMessagePostRendererV1 struct {
-	Manifests *bytes.Buffer `json:"manifests"`
+	Manifests string   `json:"manifests"`
 	// from CLI --post-renderer-args
 	ExtraArgs []string `json:"extraArgs"`
 }
 
 type OutputMessagePostRendererV1 struct {
-	Manifests *bytes.Buffer `json:"manifests"`
+	Manifests string   `json:"manifests"`
 }
 
 type ConfigPostRendererV1 struct{}
diff --git a/pkg/postrenderer/postrenderer.go b/pkg/postrenderer/postrenderer.go
index 55e6d3adf..e37ffb3f8 100644
--- a/pkg/postrenderer/postrenderer.go
+++ b/pkg/postrenderer/postrenderer.go
@@ -64,7 +64,7 @@ func (r *postRendererPlugin) Run(renderedManifests *bytes.Buffer) (*bytes.Buffer
 	input := &plugin.Input{
 		Message: schema.InputMessagePostRendererV1{
 			ExtraArgs: r.args,
-			Manifests: renderedManifests,
+			Manifests: renderedManifests.String(),
 		},
 	}
 	output, err := r.plugin.Invoke(context.Background(), input)
@@ -76,9 +76,9 @@ func (r *postRendererPlugin) Run(renderedManifests *bytes.Buffer) (*bytes.Buffer
 
 	// If the binary returned almost nothing, it's likely that it didn't
 	// successfully render anything
-	if len(bytes.TrimSpace(outputMessage.Manifests.Bytes())) == 0 {
+	if len(bytes.TrimSpace([]byte(outputMessage.Manifests))) == 0 {
 		return nil, fmt.Errorf("post-renderer %q produced empty output", r.plugin.Metadata().Name)
 	}
 
-	return outputMessage.Manifests, nil
+	return bytes.NewBufferString(outputMessage.Manifests), nil
 }