diff --git a/src/iobuf.h b/src/iobuf.h
index b806aa5e7c25d0e8a062afa743e5f3f96bfcc5fa..3fb5729b958d8133945eb34b4ab201a96c993b0a 100644
--- a/src/iobuf.h
+++ b/src/iobuf.h
@@ -90,7 +90,7 @@ iobuf_reset_mt(struct iobuf *iobuf);
 static inline bool
 iobuf_is_idle(struct iobuf *iobuf)
 {
-	return ibuf_used(&iobuf->in) == 0 && obuf_size(&iobuf->out) == 0;
+	return ibuf_used(&iobuf->in) == 0 && obuf_used(&iobuf->out) == 0;
 }
 
 /**