diff --git a/src/libcharon/encoding/generator.c b/src/libcharon/encoding/generator.c
index f898c87bd..8c3a9c94e 100644
--- a/src/libcharon/encoding/generator.c
+++ b/src/libcharon/encoding/generator.c
@@ -431,7 +431,10 @@ METHOD(generator_t, get_chunk, chunk_t,
 {
 	chunk_t data;
 
-	*lenpos = (uint32_t*)(this->buffer + this->header_length_offset);
+	if (lenpos)
+	{
+		*lenpos = (uint32_t*)(this->buffer + this->header_length_offset);
+	}
 	data = chunk_create(this->buffer, get_length(this));
 	if (this->debug)
 	{
diff --git a/src/libcharon/encoding/message.c b/src/libcharon/encoding/message.c
index b02977a02..ae7c3a3d0 100644
--- a/src/libcharon/encoding/message.c
+++ b/src/libcharon/encoding/message.c
@@ -2089,7 +2089,6 @@ METHOD(message_t, fragment, status_t,
 	host_t *src, *dst;
 	chunk_t data;
 	status_t status;
-	uint32_t *lenpos;
 	size_t len;
 
 	src = this->packet->get_source(this->packet);
@@ -2126,7 +2125,7 @@ METHOD(message_t, fragment, status_t,
 			DESTROY_IF(generator);
 			return status;
 		}
-		data = generator->get_chunk(generator, &lenpos);
+		data = generator->get_chunk(generator, NULL);
 		len = data.len + (encrypted ? encrypted->get_length(encrypted) : 0);
 	}
 
@@ -2182,7 +2181,7 @@ METHOD(message_t, fragment, status_t,
 		}
 		next = encrypted->payload_interface.get_next_type((payload_t*)encrypted);
 		encrypted->generate_payloads(encrypted, generator);
-		data = generator->get_chunk(generator, &lenpos);
+		data = generator->get_chunk(generator, NULL);
 		if (!is_encoded(this))
 		{
 			encrypted->destroy(encrypted);