diff --git a/tests/libtest/lib1521.c b/tests/libtest/lib1521.c
index 15dee2855b..27a3800642 100644
--- a/tests/libtest/lib1521.c
+++ b/tests/libtest/lib1521.c
@@ -86,20 +86,20 @@ static int geterr(const char *name, CURLcode val, int lineno)
   return (int)val;
 }
 
-curl_progress_callback progresscb;
-curl_write_callback headercb;
-curl_debug_callback debugcb;
-curl_ssl_ctx_callback ssl_ctx_cb;
-curl_ioctl_callback ioctlcb;
-curl_sockopt_callback sockoptcb;
-curl_opensocket_callback opensocketcb;
-curl_seek_callback seekcb;
-curl_sshkeycallback ssh_keycb;
-curl_chunk_bgn_callback chunk_bgn_cb;
-curl_chunk_end_callback chunk_end_cb;
-curl_fnmatch_callback fnmatch_cb;
-curl_closesocket_callback closesocketcb;
-curl_xferinfo_callback xferinfocb;
+static curl_progress_callback progresscb;
+static curl_write_callback headercb;
+static curl_debug_callback debugcb;
+static curl_ssl_ctx_callback ssl_ctx_cb;
+static curl_ioctl_callback ioctlcb;
+static curl_sockopt_callback sockoptcb;
+static curl_opensocket_callback opensocketcb;
+static curl_seek_callback seekcb;
+static curl_sshkeycallback ssh_keycb;
+static curl_chunk_bgn_callback chunk_bgn_cb;
+static curl_chunk_end_callback chunk_end_cb;
+static curl_fnmatch_callback fnmatch_cb;
+static curl_closesocket_callback closesocketcb;
+static curl_xferinfo_callback xferinfocb;
 
 int test(char *URL)
 {
diff --git a/tests/libtest/mk-lib1521.pl b/tests/libtest/mk-lib1521.pl
index 95c7135dbd..d59db0d7a1 100644
--- a/tests/libtest/mk-lib1521.pl
+++ b/tests/libtest/mk-lib1521.pl
@@ -117,20 +117,20 @@ static int geterr(const char *name, CURLcode val, int lineno)
   return (int)val;
 }
 
-curl_progress_callback progresscb;
-curl_write_callback headercb;
-curl_debug_callback debugcb;
-curl_ssl_ctx_callback ssl_ctx_cb;
-curl_ioctl_callback ioctlcb;
-curl_sockopt_callback sockoptcb;
-curl_opensocket_callback opensocketcb;
-curl_seek_callback seekcb;
-curl_sshkeycallback ssh_keycb;
-curl_chunk_bgn_callback chunk_bgn_cb;
-curl_chunk_end_callback chunk_end_cb;
-curl_fnmatch_callback fnmatch_cb;
-curl_closesocket_callback closesocketcb;
-curl_xferinfo_callback xferinfocb;
+static curl_progress_callback progresscb;
+static curl_write_callback headercb;
+static curl_debug_callback debugcb;
+static curl_ssl_ctx_callback ssl_ctx_cb;
+static curl_ioctl_callback ioctlcb;
+static curl_sockopt_callback sockoptcb;
+static curl_opensocket_callback opensocketcb;
+static curl_seek_callback seekcb;
+static curl_sshkeycallback ssh_keycb;
+static curl_chunk_bgn_callback chunk_bgn_cb;
+static curl_chunk_end_callback chunk_end_cb;
+static curl_fnmatch_callback fnmatch_cb;
+static curl_closesocket_callback closesocketcb;
+static curl_xferinfo_callback xferinfocb;
 
 int test(char *URL)
 {