diff --git a/src/colorschemer.h b/src/colorschemer.h
index b3848b993..9d6ca338c 100644
--- a/src/colorschemer.h
+++ b/src/colorschemer.h
@@ -28,7 +28,7 @@ class ColorSchemer : public QObject
     Q_PROPERTY(QAbstractItemModel *model READ model CONSTANT)
 
 public:
-    ColorSchemer(QObject *parent = nullptr);
+    explicit ColorSchemer(QObject *parent = nullptr);
     ~ColorSchemer();
 
     QAbstractItemModel *model() const;
diff --git a/src/delegatesizehelper.h b/src/delegatesizehelper.h
index 1fcbddca1..08bd42f2b 100644
--- a/src/delegatesizehelper.h
+++ b/src/delegatesizehelper.h
@@ -77,7 +77,7 @@ class DelegateSizeHelper : public QObject
     Q_PROPERTY(qreal currentWidth READ currentWidth NOTIFY currentWidthChanged)
 
 public:
-    DelegateSizeHelper(QObject *parent = nullptr);
+    explicit DelegateSizeHelper(QObject *parent = nullptr);
 
     qreal parentWidth() const;
     void setParentWidth(qreal parentWidth);
diff --git a/src/models/roomlistmodel.h b/src/models/roomlistmodel.h
index fe249cd14..335cd017e 100644
--- a/src/models/roomlistmodel.h
+++ b/src/models/roomlistmodel.h
@@ -78,7 +78,7 @@ public:
     };
     Q_ENUM(EventRoles)
 
-    RoomListModel(QObject *parent = nullptr);
+    explicit RoomListModel(QObject *parent = nullptr);
     ~RoomListModel() override;
 
     [[nodiscard]] Quotient::Connection *connection() const;
diff --git a/src/models/searchmodel.h b/src/models/searchmodel.h
index 629621fa5..f3da43d35 100644
--- a/src/models/searchmodel.h
+++ b/src/models/searchmodel.h
@@ -86,7 +86,7 @@ public:
         SourceRole,
     };
     Q_ENUM(Roles);
-    SearchModel(QObject *parent = nullptr);
+    explicit SearchModel(QObject *parent = nullptr);
 
     QString searchText() const;
     void setSearchText(const QString &searchText);
diff --git a/src/models/serverlistmodel.h b/src/models/serverlistmodel.h
index cc6b2a126..f094df69d 100644
--- a/src/models/serverlistmodel.h
+++ b/src/models/serverlistmodel.h
@@ -46,7 +46,7 @@ public:
         IsDeletableRole, /**< Whether the item can be deleted from the model. */
     };
 
-    ServerListModel(QObject *parent = nullptr);
+    explicit ServerListModel(QObject *parent = nullptr);
 
     /**
      * @brief Get the given role value at the given index.
diff --git a/src/models/sortfilterroomlistmodel.h b/src/models/sortfilterroomlistmodel.h
index 897d1db93..565789309 100644
--- a/src/models/sortfilterroomlistmodel.h
+++ b/src/models/sortfilterroomlistmodel.h
@@ -53,7 +53,7 @@ public:
     };
     Q_ENUM(RoomSortOrder)
 
-    SortFilterRoomListModel(QObject *parent = nullptr);
+    explicit SortFilterRoomListModel(QObject *parent = nullptr);
 
     void setRoomSortOrder(RoomSortOrder sortOrder);
     [[nodiscard]] RoomSortOrder roomSortOrder() const;
diff --git a/src/models/statemodel.h b/src/models/statemodel.h
index ef0ebac63..bb9cf426c 100644
--- a/src/models/statemodel.h
+++ b/src/models/statemodel.h
@@ -31,7 +31,7 @@ public:
     };
     Q_ENUM(Roles);
 
-    StateModel(QObject *parent = nullptr);
+    explicit StateModel(QObject *parent = nullptr);
 
     NeoChatRoom *room() const;
     void setRoom(NeoChatRoom *room);
diff --git a/src/models/userdirectorylistmodel.h b/src/models/userdirectorylistmodel.h
index 05d28c03c..b0ef2cd8f 100644
--- a/src/models/userdirectorylistmodel.h
+++ b/src/models/userdirectorylistmodel.h
@@ -53,7 +53,7 @@ public:
         DirectChatsRole, /**< A list of direct chat matrix IDs with the user. */
     };
 
-    UserDirectoryListModel(QObject *parent = nullptr);
+    explicit UserDirectoryListModel(QObject *parent = nullptr);
 
     [[nodiscard]] Quotient::Connection *connection() const;
     void setConnection(Quotient::Connection *conn);
diff --git a/src/models/userlistmodel.h b/src/models/userlistmodel.h
index 7f83f89c3..e55e258a5 100644
--- a/src/models/userlistmodel.h
+++ b/src/models/userlistmodel.h
@@ -47,7 +47,7 @@ public:
     };
     Q_ENUM(EventRoles)
 
-    UserListModel(QObject *parent = nullptr);
+    explicit UserListModel(QObject *parent = nullptr);
 
     [[nodiscard]] NeoChatRoom *room() const;
     void setRoom(NeoChatRoom *room);
diff --git a/src/notificationsmanager.h b/src/notificationsmanager.h
index 414ce8d5d..5bb4ed5d0 100644
--- a/src/notificationsmanager.h
+++ b/src/notificationsmanager.h
@@ -85,7 +85,7 @@ public:
 #endif
 
 private:
-    NotificationsManager(QObject *parent = nullptr);
+    explicit NotificationsManager(QObject *parent = nullptr);
 
     QHash<QString, qint64> m_initialTimestamp;
     QHash<QString, QStringList> m_oldNotifications;
diff --git a/src/trayicon_sni.h b/src/trayicon_sni.h
index 88e5b1359..85effb4f7 100644
--- a/src/trayicon_sni.h
+++ b/src/trayicon_sni.h
@@ -16,7 +16,7 @@ class TrayIcon : public KStatusNotifierItem
 {
     Q_OBJECT
 public:
-    TrayIcon(QObject *parent = nullptr);
+    explicit TrayIcon(QObject *parent = nullptr);
 
     /**
      * @brief Show the tray icon.