diff --git a/src/gui/text/qfontengine_qpf2.cpp b/src/gui/text/qfontengine_qpf2.cpp
index d636bca510..7178ef2928 100644
--- a/src/gui/text/qfontengine_qpf2.cpp
+++ b/src/gui/text/qfontengine_qpf2.cpp
@@ -44,6 +44,7 @@
 #include <QtCore/QDir>
 #include <QtCore/QBuffer>
 #include <QtCore/private/qstringiterator_p.h>
+#include <QtCore/private/qduplicatetracker_p.h>
 
 #include <QtGui/private/qpaintengine_raster_p.h>
 #include <QtGui/private/qguiapplication_p.h>
@@ -346,7 +347,7 @@ bool QFontEngineQPF2::stringToCMap(const QChar *str, int len, QGlyphLayout *glyp
     }
 
 #if defined(DEBUG_FONTENGINE)
-    QSet<QChar> seenGlyphs;
+    QDuplicateTracker<QChar> seenGlyphs;
 #endif
 
     int glyph_pos = 0;
@@ -366,10 +367,8 @@ bool QFontEngineQPF2::stringToCMap(const QChar *str, int len, QGlyphLayout *glyp
             glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
 #if 0 && defined(DEBUG_FONTENGINE)
             QChar c(uc);
-            if (!findGlyph(glyphs[glyph_pos].glyph) && !seenGlyphs.contains(c))
+            if (!findGlyph(glyphs[glyph_pos].glyph) && !seenGlyphs.hasSeen(c))
                 qDebug() << "glyph for character" << c << '/' << Qt::hex << uc << "is" << Qt::dec << glyphs[glyph_pos].glyph;
-
-            seenGlyphs.insert(c);
 #endif
             ++glyph_pos;
         }
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 949a2e075a..dbe75ebe51 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -39,6 +39,7 @@
 
 // for normalizeTypeInternal
 #include <private/qmetaobject_moc_p.h>
+#include <private/qduplicatetracker_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -1868,14 +1869,13 @@ void Moc::checkProperties(ClassDef *cdef)
     // specify get function, for compatibiliy we accept functions
     // returning pointers, or const char * for QByteArray.
     //
-    QSet<QByteArray> definedProperties;
+    QDuplicateTracker<QByteArray> definedProperties;
     for (int i = 0; i < cdef->propertyList.count(); ++i) {
         PropertyDef &p = cdef->propertyList[i];
-        if (definedProperties.contains(p.name)) {
+        if (definedProperties.hasSeen(p.name)) {
             QByteArray msg = "The property '" + p.name + "' is defined multiple times in class " + cdef->classname + ".";
             warning(msg.constData());
         }
-        definedProperties.insert(p.name);
 
         if (p.read.isEmpty() && p.member.isEmpty()) {
             if (!cdef->qPropertyMembers.contains(p.name) && !p.isQProperty) {