diff --git a/src/libkdepim/widgets/kcheckcombobox.h b/src/libkdepim/widgets/kcheckcombobox.h
--- a/src/libkdepim/widgets/kcheckcombobox.h
+++ b/src/libkdepim/widgets/kcheckcombobox.h
@@ -152,6 +152,11 @@
      */
     Q_REQUIRED_RESULT QStringList checkedItems(int role = Qt::DisplayRole) const;
 
+    /**
+     * Reimplemented to take the combo text width into account
+     */
+    QSize sizeHint() const override;
+
 public Q_SLOTS:
     /**
      * Sets the currently selected items. Items that are not found in the model
diff --git a/src/libkdepim/widgets/kcheckcombobox.cpp b/src/libkdepim/widgets/kcheckcombobox.cpp
--- a/src/libkdepim/widgets/kcheckcombobox.cpp
+++ b/src/libkdepim/widgets/kcheckcombobox.cpp
@@ -368,4 +368,19 @@
     }
 }
 
+QSize KCheckComboBox::sizeHint() const
+{
+    // sizeHint based on the items in the combo
+    QSize size = KComboBox::sizeHint();
+
+    // Ensure that we can read the complete lineedit contents
+    QSize lineeditsh = lineEdit()->sizeHint();
+    QStyleOptionComboBox opt;
+    initStyleOption(&opt);
+    lineeditsh = style()->sizeFromContents(QStyle::CT_ComboBox, &opt, lineeditsh, this); // dropdown indicator etc.
+
+    size.rwidth() = qMax(size.width(), lineeditsh.width());
+    return size;
+}
+
 #include "moc_kcheckcombobox.cpp"