diff --git a/src/libduc/buffer.c b/src/libduc/buffer.c
index dcce82d..ec1029c 100644
--- a/src/libduc/buffer.c
+++ b/src/libduc/buffer.c
@@ -47,7 +47,7 @@ void buffer_free(struct buffer *b)
 // Add item to buffer, but grow by doubling if needed
 static int buffer_put(struct buffer *b, const void *data, size_t len)
 {
-	if(b->ptr + len <= b->len) {
+	if(b->ptr + len > b->max) {
 		while(b->len + len > b->max) {
 			b->max *= 2;
 		}