diff --git a/src/gui/painting/qcolor.cpp b/src/gui/painting/qcolor.cpp
index 8e5f6e31c74..d4725829aa7 100644
--- a/src/gui/painting/qcolor.cpp
+++ b/src/gui/painting/qcolor.cpp
@@ -54,6 +54,12 @@
 
 QT_BEGIN_NAMESPACE
 
+// QColor fits into QVariant's internal storage on 64bit systems.
+// It could also fit on 32bit systems, but we cannot make it happen in Qt6, due to BC.
+#if QT_VERSION >= QT_VERSION_CHECK(7,0,0) || QT_POINTER_SIZE > 4
+static_assert(sizeof(QColor) <= QVariant::Private::MaxInternalSize);
+#endif
+
 /*!
     \internal
     If s[0..n] is a valid hex number, returns its integer value,
diff --git a/src/gui/painting/qcolor.h b/src/gui/painting/qcolor.h
index 06b264eacf9..edeba6fe61c 100644
--- a/src/gui/painting/qcolor.h
+++ b/src/gui/painting/qcolor.h
@@ -66,6 +66,8 @@ Q_GUI_EXPORT QDataStream &operator>>(QDataStream &, QColor &);
 class Q_GUI_EXPORT QColor
 {
 public:
+    // ### Qt7: make this "enum Spec: quint8 {...}" and reorder the members below for tighter
+    //          struct packing. QColor could fit into the inline storage of a QVariant on 32bit.
     enum Spec { Invalid, Rgb, Hsv, Cmyk, Hsl, ExtendedRgb };
     enum NameFormat { HexRgb, HexArgb };