diff --git a/include/common/buf.h b/include/common/buf.h
index 4208820..d39de71 100644
--- a/include/common/buf.h
+++ b/include/common/buf.h
@@ -578,7 +578,7 @@
 
 	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) &&