diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@
 set (KDE_APPLICATIONS_VERSION "${KDE_APPLICATIONS_VERSION_MAJOR}.${KDE_APPLICATIONS_VERSION_MINOR}.${KDE_APPLICATIONS_VERSION_MICRO}")
 project(Dolphin VERSION ${KDE_APPLICATIONS_VERSION})
 
-set(QT_MIN_VERSION "5.5.0")
+set(QT_MIN_VERSION "5.8.0")
 set(KF5_MIN_VERSION "5.43.0")
 set(ECM_MIN_VERSION "1.6.0")
 
diff --git a/src/dolphincontextmenu.cpp b/src/dolphincontextmenu.cpp
--- a/src/dolphincontextmenu.cpp
+++ b/src/dolphincontextmenu.cpp
@@ -428,6 +428,7 @@
 
 bool DolphinContextMenu::placeExists(const QUrl& url) const
 {
+    Q_UNUSED(url)
     // Creating up a PlacesItemModel to find out if 'url' is one of the Places
     // can be expensive because the model asks Solid for the devices which are
     // available, which can take some time.
diff --git a/src/dolphinmainwindow.cpp b/src/dolphinmainwindow.cpp
--- a/src/dolphinmainwindow.cpp
+++ b/src/dolphinmainwindow.cpp
@@ -410,6 +410,7 @@
             case QDialogButtonBox::No:
                 // Close only the current tab
                 m_tabWidget->closeTab();
+                Q_FALLTHROUGH();
             default:
                 event->ignore();
                 return;
diff --git a/src/kitemviews/kfileitemmodel.cpp b/src/kitemviews/kfileitemmodel.cpp
--- a/src/kitemviews/kfileitemmodel.cpp
+++ b/src/kitemviews/kfileitemmodel.cpp
@@ -246,7 +246,6 @@
     // Copyright (C) 2006 David Faure <faure@kde.org>
     QList<QUrl> urls;
     QList<QUrl> mostLocalUrls;
-    bool canUseMostLocalUrls = true;
     const ItemData* lastAddedItem = nullptr;
 
     for (int index : indexes) {
@@ -269,9 +268,6 @@
 
             bool isLocal;
             mostLocalUrls << item.mostLocalUrl(isLocal);
-            if (!isLocal) {
-                canUseMostLocalUrls = false;
-            }
         }
     }
 
diff --git a/src/kitemviews/kitemlistcontroller.cpp b/src/kitemviews/kitemlistcontroller.cpp
--- a/src/kitemviews/kitemlistcontroller.cpp
+++ b/src/kitemviews/kitemlistcontroller.cpp
@@ -433,8 +433,7 @@
                 }
             }
         }
-        // Fall through to the default case and add the Space to the current search string.
-
+        Q_FALLTHROUGH();  // fall through to the default case and add the Space to the current search string.
     default:
         m_keyboardManager->addKeys(event->text());
         // Make sure unconsumed events get propagated up the chain. #302329
diff --git a/src/panels/information/phononwidget.cpp b/src/panels/information/phononwidget.cpp
--- a/src/panels/information/phononwidget.cpp
+++ b/src/panels/information/phononwidget.cpp
@@ -167,7 +167,7 @@
             m_videoPlayer->hide();
         }
         emit hasVideoChanged(false);
-        // fall through
+        Q_FALLTHROUGH();
     default:
         m_stopButton->hide();
         m_playButton->show();