diff --git a/src/btstack_tlv_builder.c b/src/btstack_tlv_builder.c
index 9eb0c0c08..898594666 100644
--- a/src/btstack_tlv_builder.c
+++ b/src/btstack_tlv_builder.c
@@ -61,11 +61,11 @@ void btstack_tlv_builder_init(btstack_tlv_builder_context_t * context, uint8_t *
     context->write_pos = 0;
 }
 
-uint16_t btstack_tlv_builder_remaining_space(btstack_tlv_builder_context_t * context){
+uint16_t btstack_tlv_builder_remaining_space(const btstack_tlv_builder_context_t* context){
     return context->size - context->write_pos;
 }
 
-uint16_t btstack_tlv_builder_get_length(btstack_tlv_builder_context_t * context){
+uint16_t btstack_tlv_builder_get_length(const btstack_tlv_builder_context_t* context){
     return context->write_pos;
 }
 
diff --git a/src/btstack_tlv_builder.h b/src/btstack_tlv_builder.h
index 397cda0c3..9f9987dc2 100644
--- a/src/btstack_tlv_builder.h
+++ b/src/btstack_tlv_builder.h
@@ -73,14 +73,14 @@ void btstack_tlv_builder_init(btstack_tlv_builder_context_t * context, uint8_t *
  * @param context
  * @return number of bytes that can be added
  */
-uint16_t btstack_tlv_builder_remaining_space(btstack_tlv_builder_context_t * context);
+uint16_t btstack_tlv_builder_remaining_space(const btstack_tlv_builder_context_t* context);
 
 /**
  * @brief Get constructed event length
  * @param context
  * @return number of bytes in event
  */
-uint16_t btstack_tlv_builder_get_length(btstack_tlv_builder_context_t * context);
+uint16_t btstack_tlv_builder_get_length(const btstack_tlv_builder_context_t* context);
 
 /**
  * @brief Add tag