1 files changed, 1 insertions, 0 deletions
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 5ab625f42288..9d9f1153f4d5 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -195,6 +195,7 @@ struct CurlDownloader : public Downloader
             if (readOffset == request.data->length())
                 return 0;
             auto count = std::min(size * nitems, request.data->length() - readOffset);
+            assert(count);
             memcpy(buffer, request.data->data() + readOffset, count);
             readOffset += count;
             return count;