diff --git a/include/my_global.h b/include/my_global.h
index af1353ad..1925e4b3 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -454,7 +454,7 @@ typedef SOCKET_SIZE_TYPE size_socket;
 #ifdef _WIN32
 #define NO_DIR_LIBRARY		/* Not standar dir-library */
 #define USE_MY_STAT_STRUCT	/* For my_lib */
-#ifndef _SIZE_T_DEFINED
+#ifdef _SIZE_T_DEFINED
 typedef SSIZE_T ssize_t;
 #endif
 #endif
diff --git a/include/mysql/client_plugin.h b/include/mysql/client_plugin.h
index 13970224..a95aa61c 100644
--- a/include/mysql/client_plugin.h
+++ b/include/mysql/client_plugin.h
@@ -138,7 +138,7 @@ typedef char *(*mysql_authentication_dialog_ask_t)(struct st_mysql *mysql,
   @retval
   a pointer to the loaded plugin, or NULL in case of a failure
 */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_load_plugin(struct st_mysql *mysql, const char *name, int type,
                   int argc, ...);
 
@@ -159,7 +159,7 @@ mysql_load_plugin(struct st_mysql *mysql, const char *name, int type,
   @retval
   a pointer to the loaded plugin, or NULL in case of a failure
 */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_load_plugin_v(struct st_mysql *mysql, const char *name, int type,
                     int argc, va_list args);
 
@@ -174,7 +174,7 @@ mysql_load_plugin_v(struct st_mysql *mysql, const char *name, int type,
   @retval
   a pointer to the plugin, or NULL in case of a failure
 */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_client_find_plugin(struct st_mysql *mysql, const char *name, int type);
 
 /**
@@ -191,7 +191,7 @@ mysql_client_find_plugin(struct st_mysql *mysql, const char *name, int type);
   @retval
   a pointer to the plugin, or NULL in case of a failure
 */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_client_register_plugin(struct st_mysql *mysql,
                              struct st_mysql_client_plugin *plugin);
 
diff --git a/include/mysql_async.h b/include/mysql_async.h
index f98021e5..2728b9c1 100644
--- a/include/mysql_async.h
+++ b/include/mysql_async.h
@@ -18,10 +18,6 @@
 #ifndef MYSQL_ASYNC_H
 #define MYSQL_ASYNC_H
 
-#ifdef _WIN32
-typedef SSIZE_T ssize_t;
-#endif
-
 extern int my_connect_async(struct mysql_async_context *b, my_socket fd,
                             const struct sockaddr *name, uint namelen,
                             int vio_timeout);
diff --git a/libmariadb/client_plugin.c b/libmariadb/client_plugin.c
index b1dc6ad0..d0711e1e 100644
--- a/libmariadb/client_plugin.c
+++ b/libmariadb/client_plugin.c
@@ -306,7 +306,7 @@ void mysql_client_plugin_deinit()
 /************* public facing functions, for client consumption *********/
 
 /* see <mysql/client_plugin.h> for a full description */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_client_register_plugin(MYSQL *mysql,
                              struct st_mysql_client_plugin *plugin)
 {
@@ -335,7 +335,7 @@ mysql_client_register_plugin(MYSQL *mysql,
 
 
 /* see <mysql/client_plugin.h> for a full description */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_load_plugin_v(MYSQL *mysql, const char *name, int type,
                     int argc, va_list args)
 {
@@ -423,7 +423,7 @@ err:
 
 
 /* see <mysql/client_plugin.h> for a full description */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_load_plugin(MYSQL *mysql, const char *name, int type, int argc, ...)
 {
   struct st_mysql_client_plugin *p;
@@ -436,7 +436,7 @@ mysql_load_plugin(MYSQL *mysql, const char *name, int type, int argc, ...)
 
 
 /* see <mysql/client_plugin.h> for a full description */
-struct st_mysql_client_plugin *
+struct st_mysql_client_plugin * STDCALL
 mysql_client_find_plugin(MYSQL *mysql, const char *name, int type)
 {
   struct st_mysql_client_plugin *p;