diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5eb3a1429..98cc13987 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -66,7 +66,6 @@ endif (CMAKE_BUILD_TYPE STREQUAL "Debug")
 
 set(QBT_USE_GUI ${GUI})
 set(QBT_USE_WEBUI ${WEBUI})
-set(QBT_USES_QT5 ${QT5})
 
 configure_file(config.h.cmakein ${CMAKE_CURRENT_BINARY_DIR}/config.h)
 
diff --git a/src/base/preferences.cpp b/src/base/preferences.cpp
index 6f9b67c74..630dbe4f8 100644
--- a/src/base/preferences.cpp
+++ b/src/base/preferences.cpp
@@ -1271,20 +1271,12 @@ void Preferences::setRssMainSplitterState(const QByteArray &state)
 
 QByteArray Preferences::getSearchTabHeaderState() const
 {
-#ifdef QBT_USES_QT5
     return value("SearchTab/qt5/HeaderState").toByteArray();
-#else
-    return value("SearchTab/HeaderState").toByteArray();
-#endif
 }
 
 void Preferences::setSearchTabHeaderState(const QByteArray &state)
 {
-#ifdef QBT_USES_QT5
     setValue("SearchTab/qt5/HeaderState", state);
-#else
-    setValue("SearchTab/HeaderState", state);
-#endif
 }
 
 QStringList Preferences::getSearchEngDisabled() const
diff --git a/src/base/utils/string.cpp b/src/base/utils/string.cpp
index 801f510d7..733ae3425 100644
--- a/src/base/utils/string.cpp
+++ b/src/base/utils/string.cpp
@@ -159,12 +159,7 @@ QString Utils::String::fromStdString(const std::string &str)
 
 std::string Utils::String::toStdString(const QString &str)
 {
-#ifdef QBT_USES_QT5
     return str.toStdString();
-#else
-    QByteArray utf8 = str.toUtf8();
-    return std::string(utf8.constData(), utf8.length());
-#endif
 }
 
 // to send numbers instead of strings with suffixes
@@ -196,26 +191,5 @@ bool Utils::String::slowEquals(const QByteArray &a, const QByteArray &b)
 
 QString Utils::String::toHtmlEscaped(const QString &str)
 {
-#ifdef QBT_USES_QT5
     return str.toHtmlEscaped();
-#else
-    // code from Qt
-    QString rich;
-    const int len = str.length();
-    rich.reserve(int(len * 1.1));
-    for (int i = 0; i < len; ++i) {
-        if (str.at(i) == QLatin1Char('<'))
-            rich += QLatin1String("&lt;");
-        else if (str.at(i) == QLatin1Char('>'))
-            rich += QLatin1String("&gt;");
-        else if (str.at(i) == QLatin1Char('&'))
-            rich += QLatin1String("&amp;");
-        else if (str.at(i) == QLatin1Char('"'))
-            rich += QLatin1String("&quot;");
-        else
-            rich += str.at(i);
-    }
-    rich.squeeze();
-    return rich;
-#endif
 }
diff --git a/src/gui/categoryfilterwidget.cpp b/src/gui/categoryfilterwidget.cpp
index dd4ffe47a..0da279b25 100644
--- a/src/gui/categoryfilterwidget.cpp
+++ b/src/gui/categoryfilterwidget.cpp
@@ -161,22 +161,7 @@ void CategoryFilterWidget::callUpdateGeometry()
 
 QSize CategoryFilterWidget::sizeHint() const
 {
-#ifdef QBT_USES_QT5
     return viewportSizeHint();
-#else
-    int lastRow = model()->rowCount() - 1;
-    QModelIndex last = model()->index(lastRow, 0);
-    while ((lastRow >= 0) && isExpanded(last)) {
-        lastRow = model()->rowCount(last) - 1;
-        last = model()->index(lastRow, 0, last);
-    }
-    const QRect deepestRect = visualRect(last);
-
-    if (!deepestRect.isValid())
-        return viewport()->sizeHint();
-
-    return QSize(header()->length(), deepestRect.bottom() + 1);
-#endif
 }
 
 QSize CategoryFilterWidget::minimumSizeHint() const