diff --git a/src/pipeline.c b/src/pipeline.c
index 24ccb73..3f521e0 100644
--- a/src/pipeline.c
+++ b/src/pipeline.c
@@ -119,15 +119,21 @@ void ec3_pipeline_destroy(struct ec3_pipeline *p)
 
 enum ec3_status ec3_pipeline_encode_cluster(
 	struct ec3_pipeline *pipeline,
-	void *in,
+	const void *in,
 	size_t in_len,
 	void *out,
 	size_t out_max,
 	size_t *out_len)
 {
+	if (in_len > out_max || out_max < pipeline->p_cluster_size) {
+		return EC3_ERR_INVALID_VALUE;
+	}
+
 	b_queue_entry *cur = b_queue_first(&pipeline->p_stages);
 	enum ec3_status status = EC3_SUCCESS;
-	void *src = in;
+	memcpy(out, in, in_len);
+
+	void *src = out;
 
 	size_t stage_in_size = in_len;
 	size_t stage_out_size = 0;
@@ -170,7 +176,7 @@ enum ec3_status ec3_pipeline_encode_cluster(
 
 enum ec3_status ec3_pipeline_decode_cluster(
 	struct ec3_pipeline *pipeline,
-	void *in,
+	const void *in,
 	size_t in_len,
 	void *out,
 	size_t out_max,
diff --git a/src/pipeline.h b/src/pipeline.h
index 9d8f30b..63fba70 100644
--- a/src/pipeline.h
+++ b/src/pipeline.h
@@ -66,14 +66,14 @@ extern void ec3_pipeline_destroy(struct ec3_pipeline *p);
 
 extern enum ec3_status ec3_pipeline_encode_cluster(
 	struct ec3_pipeline *pipeline,
-	void *in,
+	const void *in,
 	size_t in_len,
 	void *out,
 	size_t out_max,
 	size_t *out_len);
 extern enum ec3_status ec3_pipeline_decode_cluster(
 	struct ec3_pipeline *pipeline,
-	void *in,
+	const void *in,
 	size_t in_len,
 	void *out,
 	size_t out_max,