diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,7 +52,6 @@
 find_package(KF5PimCommon ${PIMCOMMON_LIB_VERSION} CONFIG REQUIRED)
 find_package(KF5Libkdepim ${LIBKDEPIM_LIB_VERSION} CONFIG REQUIRED)
 find_package(KF5NewStuff ${KF5_MIN_VERSION} CONFIG REQUIRED)
-find_package(KF5WindowSystem ${KF5_MIN_VERSION} CONFIG REQUIRED)
 find_package(KF5Archive ${KF5_MIN_VERSION} CONFIG REQUIRED)
 find_package(KF5SyntaxHighlighting ${KF5_MIN_VERSION} CONFIG REQUIRED)
 find_package(KF5Mime ${KMIME_LIB_VERSION} CONFIG REQUIRED)
diff --git a/src/ksieveui/CMakeLists.txt b/src/ksieveui/CMakeLists.txt
--- a/src/ksieveui/CMakeLists.txt
+++ b/src/ksieveui/CMakeLists.txt
@@ -245,7 +245,6 @@
     KF5::MailTransport
     KF5::KIOWidgets
     KF5::NewStuff
-    KF5::WindowSystem
     Qt5::WebEngineWidgets
     KF5::PimTextEdit
     KF5::I18n
diff --git a/src/ksieveui/autocreatescripts/sievescriptlistbox.cpp b/src/ksieveui/autocreatescripts/sievescriptlistbox.cpp
--- a/src/ksieveui/autocreatescripts/sievescriptlistbox.cpp
+++ b/src/ksieveui/autocreatescripts/sievescriptlistbox.cpp
@@ -30,7 +30,6 @@
 #include <KLocalizedString>
 #include <QInputDialog>
 #include <QPushButton>
-#include <KIconLoader>
 #include <QIcon>
 
 #include <QVBoxLayout>
@@ -111,26 +110,22 @@
     mBtnTop = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnTop);
     mBtnTop->setIcon(QIcon::fromTheme(QStringLiteral("go-top")));
-    mBtnTop->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnTop->setMinimumSize(mBtnTop->sizeHint() * 1.2);
 
     mBtnUp = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnUp);
     mBtnUp->setAutoRepeat(true);
     mBtnUp->setIcon(QIcon::fromTheme(QStringLiteral("go-up")));
-    mBtnUp->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnUp->setMinimumSize(mBtnUp->sizeHint() * 1.2);
     mBtnDown = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnDown);
     mBtnDown->setAutoRepeat(true);
     mBtnDown->setIcon(QIcon::fromTheme(QStringLiteral("go-down")));
-    mBtnDown->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnDown->setMinimumSize(mBtnDown->sizeHint() * 1.2);
 
     mBtnBottom = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnBottom);
     mBtnBottom->setIcon(QIcon::fromTheme(QStringLiteral("go-bottom")));
-    mBtnBottom->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnBottom->setMinimumSize(mBtnBottom->sizeHint() * 1.2);
 
     mBtnUp->setToolTip(i18nc("Move selected filter up.", "Up"));
@@ -148,28 +143,24 @@
     mBtnNew = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnNew);
     mBtnNew->setIcon(QIcon::fromTheme(QStringLiteral("document-new")));
-    mBtnNew->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnNew->setToolTip(i18n("New Script"));
     mBtnNew->setMinimumSize(mBtnNew->sizeHint() * 1.2);
 
     mBtnDelete = new QPushButton(hb);
     hbHBoxLayout->addWidget(mBtnDelete);
     mBtnDelete->setIcon(QIcon::fromTheme(QStringLiteral("edit-delete")));
-    mBtnDelete->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnDelete->setToolTip(i18n("Delete Script"));
     mBtnDelete->setMinimumSize(mBtnDelete->sizeHint() * 1.2);
 
     mBtnRename = new QPushButton(hb);
     mBtnRename->setToolTip(i18n("Rename Script"));
     mBtnRename->setIcon(QIcon::fromTheme(QStringLiteral("edit-rename")));
-    mBtnRename->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnRename->setMinimumSize(mBtnRename->sizeHint() * 1.2);
     hbHBoxLayout->addWidget(mBtnRename);
 
     mBtnDescription = new QPushButton(hb);
     mBtnDescription->setToolTip(i18n("Edit Script Description"));
     mBtnDescription->setIcon(QIcon::fromTheme(QStringLiteral("edit-comment")));
-    mBtnDescription->setIconSize(QSize(KIconLoader::SizeSmall, KIconLoader::SizeSmall));
     mBtnDescription->setMinimumSize(mBtnDescription->sizeHint() * 1.2);
 
     hbHBoxLayout->addWidget(mBtnDescription);
diff --git a/src/ksieveui/managesievescriptsdialog.cpp b/src/ksieveui/managesievescriptsdialog.cpp
--- a/src/ksieveui/managesievescriptsdialog.cpp
+++ b/src/ksieveui/managesievescriptsdialog.cpp
@@ -26,8 +26,6 @@
 #include "util/sieveimapaccountsettings.h"
 
 #include <KLocalizedString>
-#include <kiconloader.h>
-#include <kwindowsystem.h>
 #include <QPushButton>
 #include <kmessagebox.h>
 #include <KConfigGroup>
@@ -85,8 +83,6 @@
     setModal(false);
     setAttribute(Qt::WA_GroupLeader);
     setAttribute(Qt::WA_DeleteOnClose);
-    KWindowSystem::setIcons(winId(), qApp->windowIcon().pixmap(IconSize(KIconLoader::Desktop), IconSize(KIconLoader::Desktop)),
-                            qApp->windowIcon().pixmap(IconSize(KIconLoader::Small), IconSize(KIconLoader::Small)));
     QVBoxLayout *mainLayout = new QVBoxLayout(this);
     QFrame *frame = new QFrame;
     mainLayout->addWidget(frame);
diff --git a/src/ksieveui/vacation/autotests/CMakeLists.txt b/src/ksieveui/vacation/autotests/CMakeLists.txt
--- a/src/ksieveui/vacation/autotests/CMakeLists.txt
+++ b/src/ksieveui/vacation/autotests/CMakeLists.txt
@@ -26,7 +26,6 @@
     KF5::Mime
     KF5::I18n
     KF5::IconThemes
-    KF5::WindowSystem
     KF5::MailTransport
     )
 endmacro()
diff --git a/src/ksieveui/vacation/multiimapvacationdialog.cpp b/src/ksieveui/vacation/multiimapvacationdialog.cpp
--- a/src/ksieveui/vacation/multiimapvacationdialog.cpp
+++ b/src/ksieveui/vacation/multiimapvacationdialog.cpp
@@ -23,10 +23,8 @@
 
 #include <KLocalizedString>
 #include <KSharedConfig>
-#include <kwindowsystem.h>
 #include <KMessageBox>
 #include <QTabWidget>
-#include <KIconLoader>
 
 #include <QTabBar>
 #include <QApplication>
@@ -59,10 +57,6 @@
     d->mVacationManager = manager;
 
     setWindowTitle(i18n("Configure \"Out of Office\" Replies"));
-
-    KWindowSystem::setIcons(winId(), qApp->windowIcon().pixmap(IconSize(KIconLoader::Desktop), IconSize(KIconLoader::Desktop)),
-                            qApp->windowIcon().pixmap(IconSize(KIconLoader::Small), IconSize(KIconLoader::Small)));
-
     init();
     readConfig();
 }