diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 9277c5e42ab..ded02a756a0 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -56,6 +56,20 @@ HMENU qt_getWindowsSystemMenu(const QWidget *w)
 }
 #endif
 
+static_assert(qToUnderlying(QMessageBox::ButtonRole::NRoles) ==
+              qToUnderlying(QDialogButtonBox::ButtonRole::NRoles),
+              "QMessageBox::ButtonRole and QDialogButtonBox::ButtonRole out of sync!");
+
+static_assert(std::is_same_v<std::underlying_type_t<QMessageBox::ButtonRole>,
+                             std::underlying_type_t<QDialogButtonBox::ButtonRole>>);
+
+// StandardButton enums have different underlying types
+// => qToUnderlying and std::is_same_v won't work
+// ### Qt 7: make them have the same underlying type
+static_assert(static_cast<int>(QMessageBox::StandardButton::LastButton) ==
+              static_cast<int>(QDialogButtonBox::StandardButton::LastButton),
+              "QMessageBox::StandardButton and QDialogButtonBox::StandardButton out of sync!");
+
 enum Button { Old_Ok = 1, Old_Cancel = 2, Old_Yes = 3, Old_No = 4, Old_Abort = 5, Old_Retry = 6,
               Old_Ignore = 7, Old_YesAll = 8, Old_NoAll = 9, Old_ButtonMask = 0xFF,
               NewButtonMask = 0xFFFFFC00 };
diff --git a/src/widgets/dialogs/qmessagebox.h b/src/widgets/dialogs/qmessagebox.h
index 5db4f6e67e9..897f02c5fc2 100644
--- a/src/widgets/dialogs/qmessagebox.h
+++ b/src/widgets/dialogs/qmessagebox.h
@@ -66,9 +66,6 @@ public:
         NRoles
     };
     Q_ENUM(ButtonRole)
-    static_assert(static_cast<int>(ButtonRole::NRoles) ==
-                  static_cast<int>(QDialogButtonBox::ButtonRole::NRoles),
-                  "QMessageBox::ButtonRole and QDialogButtonBox::ButtonRole out of sync!");
 
     enum StandardButton {
         // keep this in sync with QDialogButtonBox::StandardButton and QPlatformDialogHelper::StandardButton
@@ -104,10 +101,6 @@ public:
         ButtonMask         = ~FlagMask          // obsolete
     };
     Q_ENUM(StandardButton);
-    static_assert(static_cast<int>(StandardButton::LastButton) ==
-                  static_cast<int>(QDialogButtonBox::StandardButton::LastButton),
-                  "QMessageBox::StandardButton and QDialogButtonBox::StandardButton out of sync!");
-
 
 #if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
     typedef StandardButton Button;