diff --git a/lib/utils_io.c b/lib/utils_io.c
index 1facac09..d7e1cbef 100644
--- a/lib/utils_io.c
+++ b/lib/utils_io.c
@@ -184,7 +184,8 @@ ssize_t read_blockwise(int fd, size_t bsize, size_t alignment,
 out:
 	free(hangover_buf);
 	if (buf != orig_buf) {
-		memcpy(orig_buf, buf, length);
+		if (ret == length)
+			memcpy(orig_buf, buf, length);
 		free(buf);
 	}
 	return ret;