diff --git a/stream/stream.c b/stream/stream.c
index c318554feb..1f50c70344 100644
--- a/stream/stream.c
+++ b/stream/stream.c
@@ -402,7 +402,8 @@ struct bstr stream_peek(stream_t *s, int len)
         // Fill rest of the buffer.
         while (buf_valid < len) {
             int chunk = MPMAX(len - buf_valid, STREAM_BUFFER_SIZE);
-            assert(buf_valid + chunk <= TOTAL_BUFFER_SIZE);
+            if (buf_valid + chunk > TOTAL_BUFFER_SIZE)
+                chunk = TOTAL_BUFFER_SIZE - buf_valid;
             int read = stream_read_unbuffered(s, &s->buffer[buf_valid], chunk);
             if (read == 0)
                 break; // EOF