diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index b9f71ddb158..61a5542c830 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -674,6 +674,9 @@ void Moc::parse()
                 if (test(NAMESPACE)) {
                     while (test(SCOPE) || test(IDENTIFIER))
                         ;
+                    // Ignore invalid code such as: 'using namespace __identifier("x")' (QTBUG-63772)
+                    if (test(LPAREN))
+                        until(RPAREN);
                     next(SEMIC);
                 }
                 break;
diff --git a/tests/auto/tools/moc/namespace.h b/tests/auto/tools/moc/namespace.h
index 43d00e82f3e..7f1e46cd62e 100644
--- a/tests/auto/tools/moc/namespace.h
+++ b/tests/auto/tools/moc/namespace.h
@@ -76,6 +76,7 @@ namespace FooNamespace {
 
 #ifdef Q_MOC_RUN
 namespace __identifier("<AtlImplementationDetails>") {} // QTBUG-56634
+using namespace __identifier("<AtlImplementationDetails>"); // QTBUG-63772
 #endif
 
 #endif // NAMESPACE_H