diff --git a/src/testcurl/https/test_empty_response.c b/src/testcurl/https/test_empty_response.c
index 3dc5b0bb..3f53bbb4 100644
--- a/src/testcurl/https/test_empty_response.c
+++ b/src/testcurl/https/test_empty_response.c
@@ -58,7 +58,7 @@ ahc_echo (void *cls,
 
 
 static int
-testInternalSelectGet ()
+testInternalSelectGet (void)
 {
   struct MHD_Daemon *d;
   CURL *c;
diff --git a/src/testcurl/https/test_https_session_info.c b/src/testcurl/https/test_https_session_info.c
index 12208ba7..7fc97fc5 100644
--- a/src/testcurl/https/test_https_session_info.c
+++ b/src/testcurl/https/test_https_session_info.c
@@ -95,7 +95,7 @@ query_session_ahc (void *cls, struct MHD_Connection *connection,
  */
 #if LIBCURL_VERSION_NUM >= 0x072200
 static int
-test_query_session ()
+test_query_session (void)
 {
   CURL *c;
   struct CBC cbc;
diff --git a/src/testcurl/https/test_https_time_out.c b/src/testcurl/https/test_https_time_out.c
index b9e48363..cb44acb2 100644
--- a/src/testcurl/https/test_https_time_out.c
+++ b/src/testcurl/https/test_https_time_out.c
@@ -64,7 +64,7 @@ static unsigned int num_disconnects = 0;
  * Pause execution for specified number of milliseconds.
  * @param ms the number of milliseconds to sleep
  */
-void
+static void
 _MHD_sleep (uint32_t ms)
 {
 #if defined(_WIN32)
@@ -98,7 +98,7 @@ _MHD_sleep (uint32_t ms)
 }
 
 
-void
+static void
 socket_cb (void *cls,
            struct MHD_Connection *c,
            void **socket_context,
diff --git a/src/testcurl/https/tls_test_common.c b/src/testcurl/https/tls_test_common.c
index e23f1c4e..0520a24d 100644
--- a/src/testcurl/https/tls_test_common.c
+++ b/src/testcurl/https/tls_test_common.c
@@ -28,7 +28,7 @@
 
 
 FILE *
-setup_ca_cert ()
+setup_ca_cert (void)
 {
   FILE *cert_fd;