diff --git a/src/node/ui_interface.cpp b/src/node/ui_interface.cpp
index 1cbc761ae..51f14af8b 100644
--- a/src/node/ui_interface.cpp
+++ b/src/node/ui_interface.cpp
@@ -1,101 +1,103 @@
 // Copyright (c) 2010-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <node/ui_interface.h>
 
 #include <util/translation.h>
 
-#include <boost/signals2/last_value.hpp>
+#include <boost/signals2/optional_last_value.hpp>
 #include <boost/signals2/signal.hpp>
 
 CClientUIInterface uiInterface;
 
 struct UISignals {
     boost::signals2::signal<CClientUIInterface::ThreadSafeMessageBoxSig,
-                            boost::signals2::last_value<bool>>
+                            boost::signals2::optional_last_value<bool>>
         ThreadSafeMessageBox;
     boost::signals2::signal<CClientUIInterface::ThreadSafeQuestionSig,
-                            boost::signals2::last_value<bool>>
+                            boost::signals2::optional_last_value<bool>>
         ThreadSafeQuestion;
     boost::signals2::signal<CClientUIInterface::InitMessageSig> InitMessage;
     boost::signals2::signal<CClientUIInterface::NotifyNumConnectionsChangedSig>
         NotifyNumConnectionsChanged;
     boost::signals2::signal<CClientUIInterface::NotifyNetworkActiveChangedSig>
         NotifyNetworkActiveChanged;
     boost::signals2::signal<CClientUIInterface::NotifyAlertChangedSig>
         NotifyAlertChanged;
     boost::signals2::signal<CClientUIInterface::ShowProgressSig> ShowProgress;
     boost::signals2::signal<CClientUIInterface::NotifyBlockTipSig>
         NotifyBlockTip;
     boost::signals2::signal<CClientUIInterface::NotifyHeaderTipSig>
         NotifyHeaderTip;
     boost::signals2::signal<CClientUIInterface::BannedListChangedSig>
         BannedListChanged;
 };
 static UISignals g_ui_signals;
 
 #define ADD_SIGNALS_IMPL_WRAPPER(signal_name)                                  \
     boost::signals2::connection CClientUIInterface::signal_name##_connect(     \
         std::function<signal_name##Sig> fn) {                                  \
         return g_ui_signals.signal_name.connect(fn);                           \
     }
 
 ADD_SIGNALS_IMPL_WRAPPER(ThreadSafeMessageBox);
 ADD_SIGNALS_IMPL_WRAPPER(ThreadSafeQuestion);
 ADD_SIGNALS_IMPL_WRAPPER(InitMessage);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNumConnectionsChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNetworkActiveChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyAlertChanged);
 ADD_SIGNALS_IMPL_WRAPPER(ShowProgress);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyBlockTip);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyHeaderTip);
 ADD_SIGNALS_IMPL_WRAPPER(BannedListChanged);
 
 bool CClientUIInterface::ThreadSafeMessageBox(const bilingual_str &message,
                                               const std::string &caption,
                                               unsigned int style) {
-    return g_ui_signals.ThreadSafeMessageBox(message, caption, style);
+    return g_ui_signals.ThreadSafeMessageBox(message, caption, style)
+        .value_or(false);
 }
 bool CClientUIInterface::ThreadSafeQuestion(
     const bilingual_str &message, const std::string &non_interactive_message,
     const std::string &caption, unsigned int style) {
-    return g_ui_signals.ThreadSafeQuestion(message, non_interactive_message,
-                                           caption, style);
+    return g_ui_signals
+        .ThreadSafeQuestion(message, non_interactive_message, caption, style)
+        .value_or(false);
 }
 void CClientUIInterface::InitMessage(const std::string &message) {
     return g_ui_signals.InitMessage(message);
 }
 void CClientUIInterface::NotifyNumConnectionsChanged(int newNumConnections) {
     return g_ui_signals.NotifyNumConnectionsChanged(newNumConnections);
 }
 void CClientUIInterface::NotifyNetworkActiveChanged(bool networkActive) {
     return g_ui_signals.NotifyNetworkActiveChanged(networkActive);
 }
 void CClientUIInterface::NotifyAlertChanged() {
     return g_ui_signals.NotifyAlertChanged();
 }
 void CClientUIInterface::ShowProgress(const std::string &title, int nProgress,
                                       bool resume_possible) {
     return g_ui_signals.ShowProgress(title, nProgress, resume_possible);
 }
 void CClientUIInterface::NotifyBlockTip(SynchronizationState s,
                                         const CBlockIndex *i) {
     return g_ui_signals.NotifyBlockTip(s, i);
 }
 void CClientUIInterface::NotifyHeaderTip(SynchronizationState s,
                                          const CBlockIndex *i) {
     return g_ui_signals.NotifyHeaderTip(s, i);
 }
 void CClientUIInterface::BannedListChanged() {
     return g_ui_signals.BannedListChanged();
 }
 
 bool InitError(const bilingual_str &str) {
     uiInterface.ThreadSafeMessageBox(str, "", CClientUIInterface::MSG_ERROR);
     return false;
 }
 
 void InitWarning(const bilingual_str &str) {
     uiInterface.ThreadSafeMessageBox(str, "", CClientUIInterface::MSG_WARNING);
 }
diff --git a/test/lint/lint-boost-dependencies.sh b/test/lint/lint-boost-dependencies.sh
index 0601b02be..cb580b6d7 100755
--- a/test/lint/lint-boost-dependencies.sh
+++ b/test/lint/lint-boost-dependencies.sh
@@ -1,65 +1,65 @@
 #!/usr/bin/env bash
 #
 # Copyright (c) 2018 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #
 # Guard against accidental introduction of new Boost dependencies.
 
 export LC_ALL=C
 
 EXPECTED_BOOST_INCLUDES=(
     boost/algorithm/string.hpp
     boost/algorithm/string/classification.hpp
     boost/algorithm/string/replace.hpp
     boost/algorithm/string/split.hpp
     boost/date_time/posix_time/posix_time.hpp
     boost/filesystem.hpp
     boost/filesystem/fstream.hpp
     boost/multiprecision/cpp_int.hpp
     boost/multi_index/composite_key.hpp
     boost/multi_index/hashed_index.hpp
     boost/multi_index/member.hpp
     boost/multi_index/ordered_index.hpp
     boost/multi_index/sequenced_index.hpp
     boost/multi_index_container.hpp
     boost/preprocessor/cat.hpp
     boost/preprocessor/stringize.hpp
     boost/range/iterator.hpp
     boost/range/adaptor/sliced.hpp
     boost/signals2/connection.hpp
-    boost/signals2/last_value.hpp
+    boost/signals2/optional_last_value.hpp
     boost/signals2/signal.hpp
     boost/test/unit_test.hpp
     boost/thread/condition_variable.hpp
     boost/thread/mutex.hpp
     boost/thread/shared_mutex.hpp
     boost/thread/thread.hpp
     boost/variant.hpp
     boost/variant/apply_visitor.hpp
     boost/variant/static_visitor.hpp
 )
 
 for BOOST_INCLUDE in $(git grep '^#include <boost/' -- "*.cpp" "*.h" | cut -f2 -d: | cut -f2 -d'<' | cut -f1 -d'>' | sort -u); do
     IS_EXPECTED_INCLUDE=0
     for EXPECTED_BOOST_INCLUDE in "${EXPECTED_BOOST_INCLUDES[@]}"; do
         if [[ "${BOOST_INCLUDE}" == "${EXPECTED_BOOST_INCLUDE}" ]]; then
             IS_EXPECTED_INCLUDE=1
             break
         fi
     done
     if [[ ${IS_EXPECTED_INCLUDE} == 0 ]]; then
         echo "A new Boost dependency in the form of \"${BOOST_INCLUDE}\" appears to have been introduced:"
         git grep "${BOOST_INCLUDE}" -- "*.cpp" "*.h"
         echo
     fi
 done
 
 for EXPECTED_BOOST_INCLUDE in "${EXPECTED_BOOST_INCLUDES[@]}"; do
     if ! git grep -q "^#include <${EXPECTED_BOOST_INCLUDE}>" -- "*.cpp" "*.h"; then
         echo "Good job! The Boost dependency \"${EXPECTED_BOOST_INCLUDE}\" is no longer used."
         echo "Please remove it from EXPECTED_BOOST_INCLUDES in $0"
         echo "to make sure this dependency is not accidentally reintroduced."
         echo
     fi
 done