diff --git a/include/common/buf.h b/include/common/buf.h
index 420882026..d39de7112 100644
--- a/include/common/buf.h
+++ b/include/common/buf.h
@@ -578,7 +578,7 @@ static inline int b_rep_blk(struct buffer *b, char *pos, char *end, const char *
 
 	delta = len - (end - pos);
 
-	if (b_tail(b) + delta > b_wrap(b))
+	if (__b_tail(b) + delta > b_wrap(b))
 		return 0;  /* no space left */
 
 	if (b_data(b) &&
diff --git a/src/channel.c b/src/channel.c
index 13184ec3a..3bf5c5042 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -417,7 +417,7 @@ int ci_insert_line2(struct channel *c, int pos, const char *str, int len)
 
 	delta = len + 2;
 
-	if (b_tail(b) + delta >= b_wrap(b))
+	if (__b_tail(b) + delta >= b_wrap(b))
 		return 0;  /* no space left */
 
 	if (b_data(b) &&