diff --git a/src/helper/log.c b/src/helper/log.c
index ae26df5a1..380f548f4 100644
--- a/src/helper/log.c
+++ b/src/helper/log.c
@@ -401,7 +401,7 @@ char *alloc_printf(const char *format, ...)
  * fast when invoked more often than every 500ms.
  *
  */
-void keep_alive()
+void keep_alive(void)
 {
 	current_time = timeval_ms();
 	if (current_time-last_time > 1000) {
@@ -436,7 +436,7 @@ void keep_alive()
 }
 
 /* reset keep alive timer without sending message */
-void kept_alive()
+void kept_alive(void)
 {
 	current_time = timeval_ms();
 	last_time = current_time;
diff --git a/src/jtag/core.c b/src/jtag/core.c
index f12ab5924..884a74365 100644
--- a/src/jtag/core.c
+++ b/src/jtag/core.c
@@ -1872,7 +1872,7 @@ void jtag_set_verify(bool enable)
 	jtag_verify = enable;
 }
 
-bool jtag_will_verify()
+bool jtag_will_verify(void)
 {
 	return jtag_verify;
 }
@@ -1882,7 +1882,7 @@ void jtag_set_verify_capture_ir(bool enable)
 	jtag_verify_capture_ir = enable;
 }
 
-bool jtag_will_verify_capture_ir()
+bool jtag_will_verify_capture_ir(void)
 {
 	return jtag_verify_capture_ir;
 }
diff --git a/src/jtag/drivers/arm-jtag-ew.c b/src/jtag/drivers/arm-jtag-ew.c
index d35e15128..405278b9a 100644
--- a/src/jtag/drivers/arm-jtag-ew.c
+++ b/src/jtag/drivers/arm-jtag-ew.c
@@ -683,7 +683,7 @@ static int armjtagew_tap_execute(void)
 /****************************************************************************
  * JLink USB low-level functions */
 
-static struct armjtagew *armjtagew_usb_open()
+static struct armjtagew *armjtagew_usb_open(void)
 {
 	usb_init();
 
diff --git a/src/jtag/interface.c b/src/jtag/interface.c
index de132bbe8..56bbf6e51 100644
--- a/src/jtag/interface.c
+++ b/src/jtag/interface.c
@@ -45,7 +45,7 @@ void tap_set_state_impl(tap_state_t new_state)
 	state_follower = new_state;
 }
 
-tap_state_t tap_get_state()
+tap_state_t tap_get_state(void)
 {
 	return state_follower;
 }
@@ -64,7 +64,7 @@ void tap_set_end_state(tap_state_t new_end_state)
 	end_state_follower = new_end_state;
 }
 
-tap_state_t tap_get_end_state()
+tap_state_t tap_get_end_state(void)
 {
 	return end_state_follower;
 }
diff --git a/src/jtag/minidummy/minidummy.c b/src/jtag/minidummy/minidummy.c
index 7d5e6a98a..7ee206732 100644
--- a/src/jtag/minidummy/minidummy.c
+++ b/src/jtag/minidummy/minidummy.c
@@ -83,7 +83,7 @@ int interface_jtag_add_plain_dr_scan(int num_bits, const uint8_t *out_bits,
 	return ERROR_OK;
 }
 
-int interface_jtag_add_tlr()
+int interface_jtag_add_tlr(void)
 {
 	/* synchronously do the operation here */
 
diff --git a/src/jtag/zy1000/zy1000.c b/src/jtag/zy1000/zy1000.c
index 48a3d4d03..37af2f7ae 100644
--- a/src/jtag/zy1000/zy1000.c
+++ b/src/jtag/zy1000/zy1000.c
@@ -486,7 +486,7 @@ int interface_jtag_add_plain_dr_scan(int num_bits,
 	return ERROR_OK;
 }
 
-int interface_jtag_add_tlr()
+int interface_jtag_add_tlr(void)
 {
 	setCurrentState(TAP_RESET);
 	return ERROR_OK;