diff --git a/tests/libtest/lib513.c b/tests/libtest/lib513.c
index b06a3c6..bf14650 100644
--- a/tests/libtest/lib513.c
+++ b/tests/libtest/lib513.c
@@ -12,12 +12,15 @@
 
 #include "memdebug.h"
 
+#include <unistd.h>
+
 static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *userp)
 {
   (void)ptr;
   (void)size;
   (void)nmemb;
   (void)userp;
+  sleep(2);
   return CURL_READFUNC_ABORT;
 }