diff --git a/src/httprpc.cpp b/src/httprpc.cpp
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -33,7 +33,7 @@
  */
 class HTTPRPCTimer : public RPCTimerBase {
 public:
-    HTTPRPCTimer(struct event_base *eventBase, std::function<void(void)> &func,
+    HTTPRPCTimer(struct event_base *eventBase, std::function<void()> &func,
                  int64_t millis)
         : ev(eventBase, false, func) {
         struct timeval tv;
@@ -52,7 +52,7 @@
 
     const char *Name() override { return "HTTP"; }
 
-    RPCTimerBase *NewTimer(std::function<void(void)> &func,
+    RPCTimerBase *NewTimer(std::function<void()> &func,
                            int64_t millis) override {
         return new HTTPRPCTimer(base, func, millis);
     }
diff --git a/src/httpserver.h b/src/httpserver.h
--- a/src/httpserver.h
+++ b/src/httpserver.h
@@ -140,7 +140,7 @@
      * handler is the handler to call when the event is triggered.
      */
     HTTPEvent(struct event_base *base, bool deleteWhenTriggered,
-              const std::function<void(void)> &handler);
+              const std::function<void()> &handler);
     ~HTTPEvent();
 
     /**
@@ -150,7 +150,7 @@
     void trigger(struct timeval *tv);
 
     bool deleteWhenTriggered;
-    std::function<void(void)> handler;
+    std::function<void()> handler;
 
 private:
     struct event *ev;
diff --git a/src/httpserver.cpp b/src/httpserver.cpp
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -513,7 +513,7 @@
 }
 
 HTTPEvent::HTTPEvent(struct event_base *base, bool _deleteWhenTriggered,
-                     const std::function<void(void)> &_handler)
+                     const std::function<void()> &_handler)
     : deleteWhenTriggered(_deleteWhenTriggered), handler(_handler) {
     ev = event_new(base, -1, 0, httpevent_callback_fn, this);
     assert(ev);
diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1196,7 +1196,7 @@
  *  Ensure that Bitcoin is running in a usable environment with all
  *  necessary library support.
  */
-static bool InitSanityCheck(void) {
+static bool InitSanityCheck() {
     if (!ECC_InitSanityCheck()) {
         InitError(
             "Elliptic curve cryptography sanity check failure. Aborting.");
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -656,7 +656,7 @@
     //   http://qt-project.org/doc/qt-5/qmetatype.html#qRegisterMetaType)
     //   IMPORTANT if it is no longer a typedef use the normal variant above
     qRegisterMetaType<Amount>("Amount");
-    qRegisterMetaType<std::function<void(void)>>("std::function<void(void)>");
+    qRegisterMetaType<std::function<void()>>("std::function<void()>");
 
     // Need to register any types Qt doesn't know about if you intend
     // to use them with the signal/slot mechanism Qt provides. Even pointers.
diff --git a/src/qt/macnotificationhandler.h b/src/qt/macnotificationhandler.h
--- a/src/qt/macnotificationhandler.h
+++ b/src/qt/macnotificationhandler.h
@@ -18,7 +18,7 @@
     void showNotification(const QString &title, const QString &text);
 
     /** check if OS can handle UserNotifications */
-    bool hasUserNotificationCenterSupport(void);
+    bool hasUserNotificationCenterSupport();
     static MacNotificationHandler *instance();
 };
 
diff --git a/src/qt/macnotificationhandler.mm b/src/qt/macnotificationhandler.mm
--- a/src/qt/macnotificationhandler.mm
+++ b/src/qt/macnotificationhandler.mm
@@ -47,7 +47,7 @@
     }
 }
 
-bool MacNotificationHandler::hasUserNotificationCenterSupport(void)
+bool MacNotificationHandler::hasUserNotificationCenterSupport()
 {
     Class possibleClass = NSClassFromString(@"NSUserNotificationCenter");
 
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
--- a/src/qt/rpcconsole.cpp
+++ b/src/qt/rpcconsole.cpp
@@ -97,8 +97,7 @@
 class QtRPCTimerBase : public QObject, public RPCTimerBase {
     Q_OBJECT
 public:
-    QtRPCTimerBase(std::function<void(void)> &_func, int64_t millis)
-        : func(_func) {
+    QtRPCTimerBase(std::function<void()> &_func, int64_t millis) : func(_func) {
         timer.setSingleShot(true);
         connect(&timer, SIGNAL(timeout()), this, SLOT(timeout()));
         timer.start(millis);
@@ -109,14 +108,14 @@
 
 private:
     QTimer timer;
-    std::function<void(void)> func;
+    std::function<void()> func;
 };
 
 class QtRPCTimerInterface : public RPCTimerInterface {
 public:
     ~QtRPCTimerInterface() {}
     const char *Name() override { return "Qt"; }
-    RPCTimerBase *NewTimer(std::function<void(void)> &func,
+    RPCTimerBase *NewTimer(std::function<void()> &func,
                            int64_t millis) override {
         return new QtRPCTimerBase(func, millis);
     }
diff --git a/src/rpc/server.h b/src/rpc/server.h
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -146,7 +146,7 @@
      * but only GUI RPC console, and to break the dependency of pcserver on
      * httprpc.
      */
-    virtual RPCTimerBase *NewTimer(std::function<void(void)> &func,
+    virtual RPCTimerBase *NewTimer(std::function<void()> &func,
                                    int64_t millis) = 0;
 };
 
@@ -169,7 +169,7 @@
  * Run func nSeconds from now.
  * Overrides previous timer <name> (if any).
  */
-void RPCRunLater(const std::string &name, std::function<void(void)> func,
+void RPCRunLater(const std::string &name, std::function<void()> func,
                  int64_t nSeconds);
 
 typedef UniValue (*rpcfn_type)(Config &config,
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -577,7 +577,7 @@
     }
 }
 
-void RPCRunLater(const std::string &name, std::function<void(void)> func,
+void RPCRunLater(const std::string &name, std::function<void()> func,
                  int64_t nSeconds) {
     if (!timerInterface) {
         throw JSONRPCError(RPC_INTERNAL_ERROR,
diff --git a/src/test/crypto_tests.cpp b/src/test/crypto_tests.cpp
--- a/src/test/crypto_tests.cpp
+++ b/src/test/crypto_tests.cpp
@@ -229,7 +229,7 @@
     BOOST_CHECK(out == outres);
 }
 
-static std::string LongTestString(void) {
+static std::string LongTestString() {
     std::string ret;
     for (int i = 0; i < 200000; i++) {
         ret += uint8_t(i);
diff --git a/src/ui_interface.h b/src/ui_interface.h
--- a/src/ui_interface.h
+++ b/src/ui_interface.h
@@ -125,7 +125,7 @@
     boost::signals2::signal<void(bool, const CBlockIndex *)> NotifyHeaderTip;
 
     /** Banlist did change. */
-    boost::signals2::signal<void(void)> BannedListChanged;
+    boost::signals2::signal<void()> BannedListChanged;
 };
 
 /** Show warning message **/
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -5530,7 +5530,7 @@
     return true;
 }
 
-bool DumpMempool(void) {
+bool DumpMempool() {
     int64_t start = GetTimeMicros();
 
     std::map<uint256, Amount> mapDeltas;
diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -84,7 +84,7 @@
     wtxn.emplace_back(std::move(wtx));
 }
 
-static void empty_wallet(void) {
+static void empty_wallet() {
     vCoins.clear();
     wtxn.clear();
     balance = Amount::zero();