diff --git a/cmake/Qt3rdPartyLibraryHelpers.cmake b/cmake/Qt3rdPartyLibraryHelpers.cmake
index 7d40145efa1..b6efc2427df 100644
--- a/cmake/Qt3rdPartyLibraryHelpers.cmake
+++ b/cmake/Qt3rdPartyLibraryHelpers.cmake
@@ -197,7 +197,6 @@ function(qt_internal_add_3rdparty_library target)
 
     qt_internal_add_qt_repo_known_module(${target})
     qt_internal_add_target_aliases(${target})
-    _qt_internal_apply_strict_cpp(${target})
 
     qt_skip_warnings_are_errors_when_repo_unclean("${target}")
 
diff --git a/cmake/QtModuleHelpers.cmake b/cmake/QtModuleHelpers.cmake
index d92e1524fee..7576b0b1c1b 100644
--- a/cmake/QtModuleHelpers.cmake
+++ b/cmake/QtModuleHelpers.cmake
@@ -312,7 +312,6 @@ function(qt_internal_add_module target)
 
     qt_internal_add_target_aliases("${target}")
     qt_skip_warnings_are_errors_when_repo_unclean("${target}")
-    _qt_internal_apply_strict_cpp("${target}")
 
     # No need to compile Q_IMPORT_PLUGIN-containing files for non-executables.
     if(is_static_lib)
diff --git a/cmake/QtPluginHelpers.cmake b/cmake/QtPluginHelpers.cmake
index e29b638ff5b..fc036cf6a54 100644
--- a/cmake/QtPluginHelpers.cmake
+++ b/cmake/QtPluginHelpers.cmake
@@ -160,7 +160,6 @@ function(qt_internal_add_plugin target)
     qt_set_common_target_properties("${target}")
     qt_internal_add_target_aliases("${target}")
     qt_skip_warnings_are_errors_when_repo_unclean("${target}")
-    _qt_internal_apply_strict_cpp("${target}")
 
     set_target_properties("${target}" PROPERTIES
         LIBRARY_OUTPUT_DIRECTORY "${output_directory}"
diff --git a/src/corelib/global/qtypes.cpp b/src/corelib/global/qtypes.cpp
index 9de3960e2fc..9a4616b9d89 100644
--- a/src/corelib/global/qtypes.cpp
+++ b/src/corelib/global/qtypes.cpp
@@ -503,6 +503,13 @@ static_assert(sizeof(size_t) == sizeof(qsizetype)); // implied by the definition
 static_assert((std::is_same<qsizetype, qptrdiff>::value));
 static_assert(std::is_same_v<std::size_t, size_t>);
 
+#ifdef __SIZEOF_INT128__
+# ifndef QT_SUPPORTS_INT128
+#  error Qt needs to be compiled in a mode that enables INT128 \
+    if the compiler supports it in principle.
+# endif
+#endif
+
 // Check that our own typedefs are not broken.
 static_assert(sizeof(qint8) == 1, "Internal error, qint8 is misdefined");
 static_assert(sizeof(qint16)== 2, "Internal error, qint16 is misdefined");