diff --git a/libs/db/tableviewcolumn.h b/libs/db/tableviewcolumn.h
index 76ba6cd76bd6b6a3062c1656d3a99a9a4793df06..f2370bce542afb393c37d6435dd159c76b7dd84c 100644
--- a/libs/db/tableviewcolumn.h
+++ b/libs/db/tableviewcolumn.h
@@ -41,7 +41,7 @@ public:
 
     /*! Not db-aware ctor. if \a owner is true, the field \a will be owned by this column,
      so you shouldn't care about destroying this field. */
-    TableViewColumn(Field& f, bool owner = false);
+    explicit TableViewColumn(Field& f, bool owner = false);
 
     /*! Not db-aware, convenience ctor, like above. The field is created using specified parameters that are
      equal to these accepted by KexiDB::Field ctor. The column will be the owner
diff --git a/libs/db/validator.h b/libs/db/validator.h
index ce4dc2c26ea4c94e05e86f531a02a17104604cc7..af6dc197627aa29ec1df5e07688b1c16af3b1657 100644
--- a/libs/db/validator.h
+++ b/libs/db/validator.h
@@ -45,7 +45,7 @@ class CALLIGRADB_EXPORT Validator : public QValidator
 public:
     enum Result { Error = 0, Ok = 1, Warning = 2 };
 
-    Validator(QObject * parent = 0);
+    explicit Validator(QObject * parent = 0);
 
     virtual ~Validator();
 
diff --git a/libs/kopageapp/widgets/KoPABackgroundFillWidget.h b/libs/kopageapp/widgets/KoPABackgroundFillWidget.h
index a5a74be71b715fd50b06f92ea90cd9079b19d322..45c7ddebe50156cbd69040c3808f33ba5e02fd40 100644
--- a/libs/kopageapp/widgets/KoPABackgroundFillWidget.h
+++ b/libs/kopageapp/widgets/KoPABackgroundFillWidget.h
@@ -31,7 +31,7 @@ class KoPAViewBase;
 class KOPAGEAPP_EXPORT KoPABackgroundFillWidget : public KoFillConfigWidget
 {
 public:
-    KoPABackgroundFillWidget(QWidget *parent);
+    explicit KoPABackgroundFillWidget(QWidget *parent);
 
     void setView(KoPAViewBase *view);
 
diff --git a/libs/main/KoApplication.h b/libs/main/KoApplication.h
index 83ef15b29938ee9a4a234d0facba1359e91e8ff0..5427c271600fa19ffdf2cfdf4d502dacf09fbe15 100644
--- a/libs/main/KoApplication.h
+++ b/libs/main/KoApplication.h
@@ -57,7 +57,7 @@ public:
      *
      * @param nativeMimeType: the nativeMimeType of the calligra application
      */
-    KoApplication(const QByteArray &nativeMimeType);
+    explicit KoApplication(const QByteArray &nativeMimeType);
 
     /**
      *  Destructor.
diff --git a/libs/main/KoPrintingDialog_p.h b/libs/main/KoPrintingDialog_p.h
index f43222bbb177cf051e64263ad882876de60b3a5b..24364e271d1c3eb1b6bde7e982d537dcca977802 100644
--- a/libs/main/KoPrintingDialog_p.h
+++ b/libs/main/KoPrintingDialog_p.h
@@ -44,7 +44,7 @@
 
 class KoPrintingDialogPrivate {
 public:
-    KoPrintingDialogPrivate(KoPrintingDialog *dia)
+    explicit KoPrintingDialogPrivate(KoPrintingDialog *dia)
         : parent(dia),
           stop(true),
           shapeManager(0),