diff --git a/src/corelib/kernel/qsharedmemory_p.h b/src/corelib/kernel/qsharedmemory_p.h
index a2489370370..e06e7e86f34 100644
--- a/src/corelib/kernel/qsharedmemory_p.h
+++ b/src/corelib/kernel/qsharedmemory_p.h
@@ -56,14 +56,20 @@
 #include <QtCore/qstring.h>
 
 #ifdef QT_NO_SHAREDMEMORY
-# ifndef QT_NO_SYSTEMSEMAPHORE
+#    ifndef QT_NO_SYSTEMSEMAPHORE
+
+QT_BEGIN_NAMESPACE
+
 namespace QSharedMemoryPrivate
 {
     int createUnixKeyFile(const QString &fileName);
     QString makePlatformSafeKey(const QString &key,
             const QString &prefix = QLatin1String("qipc_sharedmemory_"));
 }
-#endif
+
+QT_END_NAMESPACE
+
+#    endif
 #else
 
 #include "qsystemsemaphore.h"
diff --git a/src/corelib/kernel/qsharedmemory_systemv.cpp b/src/corelib/kernel/qsharedmemory_systemv.cpp
index 8149f20724e..65ad23b9f65 100644
--- a/src/corelib/kernel/qsharedmemory_systemv.cpp
+++ b/src/corelib/kernel/qsharedmemory_systemv.cpp
@@ -109,7 +109,7 @@ key_t QSharedMemoryPrivate::handle()
      0 already existed
      1 created
   */
-int QSharedMemoryPrivate::createUnixKeyFile(const QString &fileName)
+int QT_PREPEND_NAMESPACE(QSharedMemoryPrivate)::createUnixKeyFile(const QString &fileName)
 {
     int fd = qt_safe_open(QFile::encodeName(fileName).constData(),
             O_EXCL | O_CREAT | O_RDWR, 0640);