diff --git a/src/fatfs/diskio.c b/src/fatfs/diskio.c
index 9ed4a765f3..5b5c054542 100644
--- a/src/fatfs/diskio.c
+++ b/src/fatfs/diskio.c
@@ -30,7 +30,7 @@ void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt
     else          Status &= ~STA_PROTECT;
 }
 
-void ff_disk_close()
+void ff_disk_close(void)
 {
     ReadCb = (void*)0;
     WriteCb = (void*)0;
diff --git a/src/fatfs/ff.h b/src/fatfs/ff.h
index 800e47bb39..a8c34aa453 100644
--- a/src/fatfs/ff.h
+++ b/src/fatfs/ff.h
@@ -421,7 +421,7 @@ typedef UINT (*ff_disk_read_cb)(BYTE* buff, LBA_t sector, UINT count);
 typedef UINT (*ff_disk_write_cb)(BYTE* buff, LBA_t sector, UINT count);
 
 void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt);
-void ff_disk_close();
+void ff_disk_close(void);
 
 
 #ifdef __cplusplus
diff --git a/src/fatfs/ffsystem.c b/src/fatfs/ffsystem.c
index b0409efa69..63fedf65d2 100644
--- a/src/fatfs/ffsystem.c
+++ b/src/fatfs/ffsystem.c
@@ -3,6 +3,7 @@
 /* (C)ChaN, 2018                                                          */
 /*------------------------------------------------------------------------*/
 
+#define _POSIX_SOURCE
 #define _POSIX_THREAD_SAFE_FUNCTIONS
 #include <time.h>
 
@@ -103,7 +104,7 @@ void ff_rel_grant (
 #endif
 
 
-DWORD get_fattime()
+DWORD get_fattime(void)
 {
     // TODO: return melonDS time instead of RTC??