diff --git a/gtk/Session.cc b/gtk/Session.cc
index 92bef94ad..36fdb1ed7 100644
--- a/gtk/Session.cc
+++ b/gtk/Session.cc
@@ -645,7 +645,7 @@ void Session::Impl::on_torrent_metadata_changed(tr_torrent* raw_torrent)
         [this, core = get_core_ptr(), torrent_id = tr_torrentId(raw_torrent)]()
         {
             /* update the torrent's collated name */
-            if (auto const [torrent, position] = find_torrent_by_id(torrent_id); torrent != nullptr)
+            if (auto const& [torrent, position] = find_torrent_by_id(torrent_id); torrent)
             {
                 torrent->update();
             }
@@ -912,7 +912,7 @@ void Session::Impl::torrents_added()
 
 void Session::torrent_changed(tr_torrent_id_t id)
 {
-    if (auto const [torrent, position] = impl_->find_torrent_by_id(id); torrent != nullptr)
+    if (auto const& [torrent, position] = impl_->find_torrent_by_id(id); torrent)
     {
         torrent->update();
     }
@@ -920,7 +920,7 @@ void Session::torrent_changed(tr_torrent_id_t id)
 
 void Session::remove_torrent(tr_torrent_id_t id, bool delete_files)
 {
-    if (auto const [torrent, position] = impl_->find_torrent_by_id(id); torrent != nullptr)
+    if (auto const& [torrent, position] = impl_->find_torrent_by_id(id); torrent)
     {
         /* remove from the gui */
         impl_->get_raw_model()->remove(position);
diff --git a/libtransmission/peer-msgs.cc b/libtransmission/peer-msgs.cc
index 8edef65f5..7a2d711d6 100644
--- a/libtransmission/peer-msgs.cc
+++ b/libtransmission/peer-msgs.cc
@@ -254,7 +254,7 @@ void updateDesiredRequestCount(tr_peerMsgsImpl* msgs);
 #define myLogMacro(msgs, level, text) \
     do \
     { \
-        if (true || tr_logLevelIsActive(level)) \
+        if (tr_logLevelIsActive(level)) \
         { \
             tr_logAddMessage( \
                 __FILE__, \
diff --git a/libtransmission/tr-buffer.h b/libtransmission/tr-buffer.h
index d998492ea..43578a6f4 100644
--- a/libtransmission/tr-buffer.h
+++ b/libtransmission/tr-buffer.h
@@ -378,7 +378,7 @@ public:
     }
 
     template<typename T>
-    void insert(Iterator iter, T const* const begin, T const* const end)
+    void insert([[maybe_unused]] Iterator iter, T const* const begin, T const* const end)
     {
         TR_ASSERT(iter == this->end()); // tr_buffer only supports appending
         evbuffer_add(buf_.get(), begin, end - begin);
diff --git a/libtransmission/tr-dht.cc b/libtransmission/tr-dht.cc
index c9a844033..ea7b52b5c 100644
--- a/libtransmission/tr-dht.cc
+++ b/libtransmission/tr-dht.cc
@@ -379,11 +379,11 @@ private:
 
     static auto remove_bad_pex(std::vector<tr_pex>&& pex)
     {
-        static constexpr auto IsBadPex = [](tr_pex const& pex)
+        static constexpr auto IsBadPex = [](tr_pex const& candidate)
         {
             // paper over a bug in some DHT implementation that gives port 1.
             // Xref: https://github.com/transmission/transmission/issues/527
-            return pex.port.host() == 1;
+            return candidate.port == tr_port::fromHost(1);
         };
 
         pex.erase(std::remove_if(std::begin(pex), std::end(pex), IsBadPex), std::end(pex));
diff --git a/qt/DetailsDialog.cc b/qt/DetailsDialog.cc
index 99d74f156..33f71e6b5 100644
--- a/qt/DetailsDialog.cc
+++ b/qt/DetailsDialog.cc
@@ -1311,7 +1311,7 @@ void DetailsDialog::onIdleModeChanged(int index)
 void DetailsDialog::onIdleLimitChanged()
 {
     //: Spin box format, "Stop seeding if idle for: [ 5 minutes ]"
-    auto const units_format = QT_TRANSLATE_N_NOOP("DetailsDialog", "%1 minute(s)");
+    auto const* const units_format = QT_TRANSLATE_N_NOOP("DetailsDialog", "%1 minute(s)");
     auto const placeholder = QStringLiteral("%1");
     Utils::updateSpinBoxFormat(ui_.idleSpin, "DetailsDialog", units_format, placeholder);
 }
diff --git a/qt/Filters.h b/qt/Filters.h
index 3313055b9..e47eed30b 100644
--- a/qt/Filters.h
+++ b/qt/Filters.h
@@ -37,12 +37,13 @@ public:
 
     /* The Torrent properties that can affect this filter.
        When one of these changes, it's time to refilter. */
-    static Torrent::fields_t constexpr TorrentFields = //
-        (uint64_t(1) << Torrent::ERROR) | //
-        (uint64_t(1) << Torrent::IS_FINISHED) | //
-        (uint64_t(1) << Torrent::PEERS_GETTING_FROM_US) | //
-        (uint64_t(1) << Torrent::PEERS_SENDING_TO_US) | //
-        (uint64_t(1) << Torrent::STATUS);
+    static constexpr auto TorrentFields = Torrent::fields_t{
+        (uint64_t{ 1 } << Torrent::TORRENT_ERROR) | //
+        (uint64_t{ 1 } << Torrent::IS_FINISHED) | //
+        (uint64_t{ 1 } << Torrent::PEERS_GETTING_FROM_US) | //
+        (uint64_t{ 1 } << Torrent::PEERS_SENDING_TO_US) | //
+        (uint64_t{ 1 } << Torrent::STATUS) //
+    };
 
     static bool test(Torrent const& tor, int mode);
 
diff --git a/qt/PrefsDialog.cc b/qt/PrefsDialog.cc
index 4065c14a2..996b4c78e 100644
--- a/qt/PrefsDialog.cc
+++ b/qt/PrefsDialog.cc
@@ -550,7 +550,7 @@ void PrefsDialog::initPrivacyTab()
 void PrefsDialog::onIdleLimitChanged()
 {
     //: Spin box format, "Stop seeding if idle for: [ 5 minutes ]"
-    auto const units_format = QT_TRANSLATE_N_NOOP("PrefsDialog", "%1 minute(s)");
+    auto const* const units_format = QT_TRANSLATE_N_NOOP("PrefsDialog", "%1 minute(s)");
     auto const placeholder = QStringLiteral("%1");
     Utils::updateSpinBoxFormat(ui_.idleLimitSpin, "PrefsDialog", units_format, placeholder);
 }
@@ -576,7 +576,7 @@ void PrefsDialog::initSeedingTab()
 void PrefsDialog::onQueueStalledMinutesChanged()
 {
     //: Spin box format, "Download is inactive if data sharing stopped: [ 5 minutes ago ]"
-    auto const units_format = QT_TRANSLATE_N_NOOP("PrefsDialog", "%1 minute(s) ago");
+    auto const* const units_format = QT_TRANSLATE_N_NOOP("PrefsDialog", "%1 minute(s) ago");
     auto const placeholder = QStringLiteral("%1");
     Utils::updateSpinBoxFormat(ui_.queueStalledMinutesSpin, "PrefsDialog", units_format, placeholder);
 }
diff --git a/qt/Torrent.cc b/qt/Torrent.cc
index 78fe3d081..e959bbe8a 100644
--- a/qt/Torrent.cc
+++ b/qt/Torrent.cc
@@ -210,7 +210,7 @@ Torrent::fields_t Torrent::update(tr_quark const* keys, tr_variant const* const*
             HANDLE_KEY(downloadLimited, download_limited, DOWNLOAD_LIMITED)
             HANDLE_KEY(downloadedEver, downloaded_ever, DOWNLOADED_EVER)
             HANDLE_KEY(editDate, edit_date, EDIT_DATE)
-            HANDLE_KEY(error, error, ERROR)
+            HANDLE_KEY(error, error, TORRENT_ERROR)
             HANDLE_KEY(eta, eta, ETA)
             HANDLE_KEY(fileStats, files, FILES)
             HANDLE_KEY(files, files, FILES)
@@ -269,7 +269,7 @@ Torrent::fields_t Torrent::update(tr_quark const* keys, tr_variant const* const*
             HANDLE_KEY(comment, comment, COMMENT)
             HANDLE_KEY(creator, creator, CREATOR)
             HANDLE_KEY(downloadDir, download_dir, DOWNLOAD_DIR)
-            HANDLE_KEY(errorString, error_string, ERROR_STRING)
+            HANDLE_KEY(errorString, error_string, TORRENT_ERROR_STRING)
 
 #undef HANDLE_KEY
         default:
diff --git a/qt/Torrent.h b/qt/Torrent.h
index affbcd580..ebc795678 100644
--- a/qt/Torrent.h
+++ b/qt/Torrent.h
@@ -27,10 +27,6 @@
 #include "IconCache.h"
 #include "Speed.h"
 
-#ifdef ERROR
-#undef ERROR
-#endif
-
 class QPixmap;
 
 class Prefs;
@@ -572,8 +568,8 @@ public:
         DOWNLOAD_LIMITED,
         DOWNLOAD_SPEED,
         EDIT_DATE,
-        ERROR,
-        ERROR_STRING,
+        TORRENT_ERROR,
+        TORRENT_ERROR_STRING,
         ETA,
         FAILED_EVER,
         FILE_COUNT,