diff --git a/ccid/src/ccid.c b/ccid/src/ccid.c
index 8e75666..34f65c4 100644
--- a/ccid/src/ccid.c
+++ b/ccid/src/ccid.c
@@ -146,7 +146,7 @@ int ccid_initialize(int reader_id, const char *cdriver, int verbose)
     return SC_SUCCESS;
 }
 
-void ccid_shutdown()
+void ccid_shutdown(void)
 {
     int i;
     for (i = 0; i < sizeof *card_in_slot; i++) {
diff --git a/ccid/src/ccid.h b/ccid/src/ccid.h
index e645f7d..76941c5 100644
--- a/ccid/src/ccid.h
+++ b/ccid/src/ccid.h
@@ -266,7 +266,7 @@ struct hid_class_descriptor {
 } __attribute__ ((packed));
 
 int ccid_initialize(int reader_id, const char *cdriver, int verbose);
-void ccid_shutdown();
+void ccid_shutdown(void);
 
 int ccid_parse_bulkin(const __u8* inbuf, size_t inlen, __u8** outbuf);
 int ccid_parse_control(struct usb_ctrlrequest *setup, __u8 **outbuf);
diff --git a/ccid/src/usb.c b/ccid/src/usb.c
index 63e1ae2..b0702da 100644
--- a/ccid/src/usb.c
+++ b/ccid/src/usb.c
@@ -1142,7 +1142,7 @@ error:
     pthread_exit(0);
 }
 
-static void start_io ()
+static void start_io (void)
 {
     //int tmp;
 	sigset_t	allsig, oldsig;
diff --git a/picc_to_pcsc/src/picc_to_pcsc.c b/picc_to_pcsc/src/picc_to_pcsc.c
index befe0ae..06aea47 100644
--- a/picc_to_pcsc/src/picc_to_pcsc.c
+++ b/picc_to_pcsc/src/picc_to_pcsc.c
@@ -87,7 +87,7 @@ char* perform_initialization(int num)
 }
 
 
-void setup() {
+void setup(void) {
 	/*setup environment, open device, set global filehandle*/
 	DWORD dwActiveProtocol;
    	LONG pcsc_result;
@@ -130,7 +130,7 @@ void printHex(char *title, unsigned char *msg, unsigned int length) {
 	printf("\n");
 }
 
-void cleanup() {
+void cleanup(void) {
 	int releaseContext;	
 	/*Power down card*/
 	SCardDisconnect(hcard, SCARD_UNPOWER_CARD);
diff --git a/picc_to_pcsc/src/picc_to_pcsc.h b/picc_to_pcsc/src/picc_to_pcsc.h
index 5a80c2f..c71fbbd 100644
--- a/picc_to_pcsc/src/picc_to_pcsc.h
+++ b/picc_to_pcsc/src/picc_to_pcsc.h
@@ -17,8 +17,8 @@ void checkSig(int signo);
 unsigned int read_from_device(unsigned char *inputBuffer);
 int transmit_to_pcsc(unsigned char *inputBuffer, unsigned int inputLength, unsigned char *outputBuffer, unsigned int *outputLength);
 void write_to_device(unsigned char *buffer, unsigned int msglength);
-void setup();
-void cleanup();
+void setup(void);
+void cleanup(void);
 void printHex(char *title, unsigned char *msg, unsigned int length); 
 
 #endif
diff --git a/virtualsmartcard/src/vpcd/ifd.c b/virtualsmartcard/src/vpcd/ifd.c
index 80ff153..657ba67 100644
--- a/virtualsmartcard/src/vpcd/ifd.c
+++ b/virtualsmartcard/src/vpcd/ifd.c
@@ -20,7 +20,7 @@ IO_Create_Channel(DWORD channelid)
 }
 
 RESPONSECODE
-IO_Close_Channel()
+IO_Close_Channel(void)
 {
     Log1(PCSC_LOG_DEBUG, "");
     RESPONSECODE r = IFD_Eject_ICC();
@@ -107,14 +107,14 @@ IFD_Power_ICC(DWORD a)
 }
 
 RESPONSECODE
-IFD_Swallow_ICC()
+IFD_Swallow_ICC(void)
 {
     Log1(PCSC_LOG_DEBUG, "");
     return IFD_NOT_SUPPORTED;
 }
 
 RESPONSECODE
-IFD_Eject_ICC()
+IFD_Eject_ICC(void)
 {
     if (vicc_eject() < 0) {
         return IFD_COMMUNICATION_ERROR;
@@ -123,7 +123,7 @@ IFD_Eject_ICC()
 }
 
 RESPONSECODE
-IFD_Confiscate_ICC()
+IFD_Confiscate_ICC(void)
 {
     Log1(PCSC_LOG_DEBUG, "");
     return IFD_NOT_SUPPORTED;
@@ -151,7 +151,7 @@ IFD_Transmit_to_ICC(SCARD_IO_HEADER SendPci, PUCHAR TxBuffer, DWORD TxLength,
 }
 
 RESPONSECODE
-IFD_Is_ICC_Present()
+IFD_Is_ICC_Present(void)
 {
     switch (vicc_present()) {
         case 0:  return IFD_ICC_NOT_PRESENT;
@@ -164,7 +164,7 @@ IFD_Is_ICC_Present()
 }
 
 RESPONSECODE
-IFD_Is_ICC_Absent()
+IFD_Is_ICC_Absent(void)
 {
     return IFD_Is_ICC_Present();
 }
diff --git a/virtualsmartcard/src/vpcd/vpcd.c b/virtualsmartcard/src/vpcd/vpcd.c
index a503284..94636b0 100644
--- a/virtualsmartcard/src/vpcd/vpcd.c
+++ b/virtualsmartcard/src/vpcd/vpcd.c
@@ -155,7 +155,7 @@ int recvFromVICC(char** buffer) {
     return size;
 }
 
-int vicc_eject() {
+int vicc_eject(void) {
     if (client_sock > 0) {
         client_sock = close(client_sock);
         if (client_sock < 0) {
@@ -165,7 +165,7 @@ int vicc_eject() {
     return 0;
 }
 
-int vicc_init() {
+int vicc_init(void) {
     server_sock = opensock(VPCDPORT);
     if (server_sock < 0)
         return -1;
@@ -173,7 +173,7 @@ int vicc_init() {
     return 0;
 }
 
-int vicc_exit() {
+int vicc_exit(void) {
     if (server_sock > 0) {
         server_sock = close(server_sock);
         if (server_sock < 0) return -1;
@@ -188,7 +188,7 @@ int vicc_transmit(int apdu_len, const char *apdu, char **rapdu) {
     return recvFromVICC(rapdu);
 }
 
-int vicc_present() {
+int vicc_present(void) {
     if (client_sock > 0) return 1;
     else {
         /* Wait up to one microsecond. */
@@ -205,17 +205,17 @@ int vicc_getatr(char** atr) {
     return vicc_transmit(VPCD_CTRL_LEN, &i, atr);
 }
 
-int vicc_poweron() {
+int vicc_poweron(void) {
     char i = VPCD_CTRL_ON;
     return sendToVICC(VPCD_CTRL_LEN, &i);
 }
 
-int vicc_poweroff() {
+int vicc_poweroff(void) {
     char i = VPCD_CTRL_OFF;
     return sendToVICC(VPCD_CTRL_LEN, &i);
 }
 
-int vicc_reset() {
+int vicc_reset(void) {
     char i = VPCD_CTRL_RESET;
     return sendToVICC(VPCD_CTRL_LEN, &i);
 }
diff --git a/virtualsmartcard/src/vpcd/vpcd.h b/virtualsmartcard/src/vpcd/vpcd.h
index c71ed33..88d0b84 100644
--- a/virtualsmartcard/src/vpcd/vpcd.h
+++ b/virtualsmartcard/src/vpcd/vpcd.h
@@ -45,15 +45,15 @@ int sendToVICC(uint16_t size, const char* buffer);
  */
 int recvFromVICC(char** buffer);
 
-int vicc_eject();
-int vicc_init();
-int vicc_exit();
+int vicc_eject(void);
+int vicc_init(void);
+int vicc_exit(void);
 int vicc_transmit(int apdu_len, const char *apdu, char **rapdu);
 int vicc_getatr(char** atr);
-int vicc_present();
-int vicc_poweron();
-int vicc_poweroff();
-int vicc_reset();
+int vicc_present(void);
+int vicc_poweron(void);
+int vicc_poweroff(void);
+int vicc_reset(void);
 
 #ifdef  __cplusplus
 }