diff --git a/buffer.c b/buffer.c
index 8f751a42..d9bc8928 100644
--- a/buffer.c
+++ b/buffer.c
@@ -118,13 +118,13 @@ evbuffer_free(struct evbuffer *buffer)
 }
 
 size_t
-evbuffer_get_length(struct evbuffer *buffer)
+evbuffer_get_length(const struct evbuffer *buffer)
 {
 	return (buffer->total_len);
 }
 
 size_t
-evbuffer_get_contiguous_space(struct evbuffer *buf)
+evbuffer_get_contiguous_space(const struct evbuffer *buf)
 {
 	struct evbuffer_chain *chain = buf->first;
 
diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index 4f34a3b3..1194c056 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -93,7 +93,7 @@ void evbuffer_free(struct evbuffer *buf);
   @param buf pointer to the evbuffer
   @return the number of bytes stored in the event buffer
 */
-size_t evbuffer_get_length(struct evbuffer *buf);
+size_t evbuffer_get_length(const struct evbuffer *buf);
 
 /**
    Returns the number of contiguous available bytes in the first buffer chain.
@@ -107,7 +107,7 @@ size_t evbuffer_get_length(struct evbuffer *buf);
    @return 0 if no data is available, otherwise the number of available bytes
      in the first buffer chain.
 */
-size_t evbuffer_get_contiguous_space(struct evbuffer *buf);
+size_t evbuffer_get_contiguous_space(const struct evbuffer *buf);
 
 /**
   Expands the available space in an event buffer.