diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index a8a1fb372ca..461382092ec 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -595,6 +595,12 @@ void Moc::parse()
                     QByteArray nsName = lexem();
                     QByteArrayList nested;
                     while (test(SCOPE)) {
+                        /* treat (C++20's) namespace A::inline B {} as A::B
+                           this is mostly to not break compilation when encountering such
+                           a construct in a header; the interaction of Qt's meta-macros with
+                           inline namespaces is still rather poor.
+                        */
+                        test(INLINE);
                         next(IDENTIFIER);
                         nested.append(nsName);
                         nsName = lexem();
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index 7dc4f2ccdce..8862b0daf2d 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -64,6 +64,15 @@
 const char *string_hash_hash = STRING_HASH_HASH("baz");
 #endif
 
+#if defined(Q_MOC_RUN) || __cplusplus > 202002L
+/* Check that nested inline namespaces are at least not causing moc to break.
+   Check it even outside of C++20 mode as moc gets passed the  wrong __cplusplus version
+   and also to increase coverage, given how few C++20 configurations exist in the CI at the time
+   of writing this comment.
+*/
+namespace A::inline B {}
+#endif
+
 Q_DECLARE_METATYPE(const QMetaObject*);
 
 #define TESTEXPORTMACRO Q_DECL_EXPORT