diff --git a/audio/control.c b/audio/control.c
index 95c0406..d6890de 100644
--- a/audio/control.c
+++ b/audio/control.c
@@ -200,7 +200,7 @@ static GSList *avctp_callbacks = NULL;
 
 static void auth_cb(DBusError *derr, void *user_data);
 
-static sdp_record_t *avrcp_ct_record()
+static sdp_record_t *avrcp_ct_record(void)
 {
 	sdp_list_t *svclass_id, *pfseq, *apseq, *root;
 	uuid_t root_uuid, l2cap, avctp, avrct;
@@ -264,7 +264,7 @@ static sdp_record_t *avrcp_ct_record()
 	return record;
 }
 
-static sdp_record_t *avrcp_tg_record()
+static sdp_record_t *avrcp_tg_record(void)
 {
 	sdp_list_t *svclass_id, *pfseq, *apseq, *root;
 	uuid_t root_uuid, l2cap, avctp, avrtg;
diff --git a/audio/telephony-ofono.c b/audio/telephony-ofono.c
index 6f5685b..c00637e 100644
--- a/audio/telephony-ofono.c
+++ b/audio/telephony-ofono.c
@@ -259,7 +259,7 @@ static int release_call(struct voice_call *vc)
 						NULL, NULL, DBUS_TYPE_INVALID);
 }
 
-static int release_answer_calls()
+static int release_answer_calls(void)
 {
 	DBG("");
 	return send_method_call(OFONO_BUS_NAME, modem_obj_path,
diff --git a/health/hdp.c b/health/hdp.c
index d53ea80..0f8d6fa 100644
--- a/health/hdp.c
+++ b/health/hdp.c
@@ -260,7 +260,7 @@ static gint cmp_chan_mdl(gconstpointer a, gconstpointer mdl)
 	return -1;
 }
 
-static uint8_t get_app_id()
+static uint8_t get_app_id(void)
 {
 	uint8_t id = next_app_id;
 
@@ -1288,7 +1288,7 @@ static void mcl_uncached(struct mcap_mcl *mcl, gpointer data)
 	DBG("Mcl uncached %s", path);
 }
 
-static void check_devices_mcl()
+static void check_devices_mcl(void)
 {
 	struct hdp_device *dev;
 	GSList *l, *to_delete = NULL;
@@ -1471,7 +1471,7 @@ static void destroy_create_dc_data(gpointer data)
 	hdp_create_data_unref(dc_data);
 }
 
-static void *generate_echo_packet()
+static void *generate_echo_packet(void)
 {
 	uint8_t *buf;
 	int i;
@@ -2193,7 +2193,7 @@ int hdp_manager_start(DBusConnection *conn)
 	return 0;
 }
 
-void hdp_manager_stop()
+void hdp_manager_stop(void)
 {
 	g_dbus_unregister_interface(connection, MANAGER_PATH, HEALTH_MANAGER);
 
diff --git a/health/hdp.h b/health/hdp.h
index 3cf87ca..642ed53 100644
--- a/health/hdp.h
+++ b/health/hdp.h
@@ -30,6 +30,6 @@ int hdp_device_register(DBusConnection *conn, struct btd_device *device);
 void hdp_device_unregister(struct btd_device *device);
 
 int hdp_manager_start(DBusConnection *conn);
-void hdp_manager_stop();
+void hdp_manager_stop(void);
 
 gboolean hdp_set_mcl_cb(struct hdp_device *device, GError **err);
diff --git a/src/sdp-xml.c b/src/sdp-xml.c
index 3aa9df0..f821376 100644
--- a/src/sdp-xml.c
+++ b/src/sdp-xml.c
@@ -704,7 +704,7 @@ sdp_data_t *sdp_xml_parse_nil(const char *data)
 
 #define DEFAULT_XML_DATA_SIZE 1024
 
-struct sdp_xml_data *sdp_xml_data_alloc()
+struct sdp_xml_data *sdp_xml_data_alloc(void)
 {
 	struct sdp_xml_data *elem;
 
diff --git a/src/sdp-xml.h b/src/sdp-xml.h
index 7031276..db7db30 100644
--- a/src/sdp-xml.h
+++ b/src/sdp-xml.h
@@ -49,7 +49,7 @@ struct sdp_xml_data {
 	/* TODO: What is it used for? */
 };
 
-struct sdp_xml_data *sdp_xml_data_alloc();
+struct sdp_xml_data *sdp_xml_data_alloc(void);
 void sdp_xml_data_free(struct sdp_xml_data *elem);
 struct sdp_xml_data *sdp_xml_data_expand(struct sdp_xml_data *elem);
 
diff --git a/src/sdpd-service.c b/src/sdpd-service.c
index fe4de6a..96799ed 100644
--- a/src/sdpd-service.c
+++ b/src/sdpd-service.c
@@ -65,7 +65,7 @@ static const int sdpServerVnumEntries = 1;
  * seconds. Used for updating the service db state
  * attribute of the service record of the SDP server
  */
-uint32_t sdp_get_time()
+uint32_t sdp_get_time(void)
 {
 	/*
 	 * To handle failure in gettimeofday, so an old
diff --git a/src/sdpd.h b/src/sdpd.h
index dc7a256..471e9cc 100644
--- a/src/sdpd.h
+++ b/src/sdpd.h
@@ -83,7 +83,7 @@ sdp_list_t *sdp_get_access_list(void);
 int sdp_check_access(uint32_t handle, bdaddr_t *device);
 uint32_t sdp_next_handle(void);
 
-uint32_t sdp_get_time();
+uint32_t sdp_get_time(void);
 
 #define SDP_SERVER_COMPAT (1 << 0)
 #define SDP_SERVER_MASTER (1 << 1)