diff --git a/src/plugins/qt4projectmanager/debugginghelperbuildtask.cpp b/src/plugins/qt4projectmanager/debugginghelperbuildtask.cpp
index 727abce72b633eb80c80aec63509c061ad4ff2c9..cd07bd4ae3afb52e6af3b39536965133c425b86e 100644
--- a/src/plugins/qt4projectmanager/debugginghelperbuildtask.cpp
+++ b/src/plugins/qt4projectmanager/debugginghelperbuildtask.cpp
@@ -185,8 +185,8 @@ bool DebuggingHelperBuildTask::buildDebuggingHelper(QFutureInterface<void> &futu
             return false;
 
         QStringList qmakeArgs;
-        qmakeArgs << QLatin1String("INCLUDEPATH+=") + qmlDebuggingDirectory + "/include";
-        qmakeArgs << QLatin1String("LIBS+=-L") + qmlDebuggingDirectory;
+        qmakeArgs << QLatin1String("INCLUDEPATH+=\"\\\"") + qmlDebuggingDirectory + "include\\\"\"";
+        qmakeArgs << QLatin1String("LIBS+=-L\"\\\"") + qmlDebuggingDirectory + QLatin1String("\\\"\"");
 
         if (!QmlObserverTool::build(qmlObserverDirectory, m_makeCommand, m_qmakeCommand, m_mkspec,
                                     m_environment, m_target, qmakeArgs, output, &m_errorMessage))