diff --git a/include/my_dbug.h b/include/my_dbug.h
index bcf2015466d..f4c854bc10c 100644
--- a/include/my_dbug.h
+++ b/include/my_dbug.h
@@ -58,7 +58,7 @@ extern  void _db_end_(void);
 extern  void _db_lock_file_(void);
 extern  void _db_unlock_file_(void);
 extern  FILE *_db_fp_(void);
-extern  void _db_flush_();
+extern void _db_flush_(void);
 extern void dbug_swap_code_state(void **code_state_store);
 extern void dbug_free_code_state(void **code_state_store);
 extern  const char* _db_get_func_(void);
@@ -123,7 +123,7 @@ extern  const char* _db_get_func_(void);
 #ifdef __WIN__
 #define DBUG_SUICIDE() DBUG_ABORT()
 #else
-extern void _db_suicide_();
+extern void _db_suicide_(void);
 #define DBUG_SUICIDE() (_db_flush_(), _db_suicide_())
 #endif
 
diff --git a/include/my_global.h b/include/my_global.h
index e9a472e686e..3027eed7e17 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -555,7 +555,7 @@ typedef int	my_socket;	/* File descriptor for sockets */
 /* Type for fuctions that handles signals */
 #define sig_handler RETSIGTYPE
 C_MODE_START
-typedef void	(*sig_return)();/* Returns type from signal */
+typedef void (*sig_return)(void); /* Returns type from signal */
 C_MODE_END
 #if defined(__GNUC__) && !defined(_lint)
 typedef char	pchar;		/* Mixed prototypes can take char */
diff --git a/include/my_pthread.h b/include/my_pthread.h
index 7770c28f45f..bb4d0c88ebd 100644
--- a/include/my_pthread.h
+++ b/include/my_pthread.h
@@ -701,8 +701,8 @@ extern void my_thread_end(void);
 extern const char *my_thread_name(void);
 extern my_thread_id my_thread_dbug_id(void);
 extern int pthread_dummy(int);
-extern void my_mutex_init();
-extern void my_mutex_end();
+extern void my_mutex_init(void);
+extern void my_mutex_end(void);
 
 /* All thread specific variables are in the following struct */
 
@@ -745,8 +745,8 @@ struct st_my_thread_var
 };
 
 extern struct st_my_thread_var *_my_thread_var(void) __attribute__ ((const));
-extern void **my_thread_var_dbug();
-extern safe_mutex_t **my_thread_var_mutex_in_use();
+extern void **my_thread_var_dbug(void);
+extern safe_mutex_t **my_thread_var_mutex_in_use(void);
 extern uint my_thread_end_wait_time;
 extern my_bool safe_mutex_deadlock_detector;
 #define my_thread_var (_my_thread_var())
diff --git a/include/my_sys.h b/include/my_sys.h
index 741116a1dd5..036084a0ae0 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -642,7 +642,7 @@ extern void     my_osmaperr(unsigned long last_error);
 #endif
 
 extern void init_glob_errs(void);
-extern const char** get_global_errmsgs();
+extern const char** get_global_errmsgs(void);
 extern void wait_for_free_space(const char *filename, int errors);
 extern FILE *my_fopen(const char *FileName,int Flags,myf MyFlags);
 extern FILE *my_fdopen(File Filedes,const char *name, int Flags,myf MyFlags);
@@ -667,7 +667,7 @@ extern void my_printf_error(uint my_err, const char *format,
                             ATTRIBUTE_FORMAT(printf, 2, 4);
 extern void my_printv_error(uint error, const char *format, myf MyFlags,
                             va_list ap);
-extern int my_error_register(const char** (*get_errmsgs) (),
+extern int my_error_register(const char** (*get_errmsgs) (void),
                              uint first, uint last);
 extern const char **my_error_unregister(uint first, uint last);
 extern void my_message(uint my_err, const char *str,myf MyFlags);
@@ -885,12 +885,12 @@ extern uint my_set_max_open_files(uint files);
 void my_free_open_file_info(void);
 
 extern my_bool my_gethwaddr(uchar *to);
-extern int my_getncpus();
+extern int my_getncpus(void);
 
 #define HRTIME_RESOLUTION               1000000ULL  /* microseconds */
 typedef struct {ulonglong val;} my_hrtime_t;
-void my_time_init();
-extern my_hrtime_t my_hrtime();
+void my_time_init(void);
+extern my_hrtime_t my_hrtime(void);
 extern ulonglong my_interval_timer(void);
 extern ulonglong my_getcputime(void);
 
@@ -949,7 +949,7 @@ int my_msync(int, void *, size_t, int);
 void my_uuid_init(ulong seed1, ulong seed2);
 void my_uuid(uchar *guid);
 void my_uuid2str(const uchar *guid, char *s);
-void my_uuid_end();
+void my_uuid_end(void);
 
 /* character sets */
 extern void my_charset_loader_init_mysys(MY_CHARSET_LOADER *loader);