diff --git a/Modules/FindQt4.cmake b/Modules/FindQt4.cmake
index 46a03550b..24747f732 100644
--- a/Modules/FindQt4.cmake
+++ b/Modules/FindQt4.cmake
@@ -738,6 +738,11 @@ _qt4_find_qmake("${_QT4_QMAKE_NAMES}" QT_QMAKE_EXECUTABLE QTVERSION)
 
 if (QT_QMAKE_EXECUTABLE AND QTVERSION)
 
+  if (QT_QMAKE_EXECUTABLE_LAST)
+    string(COMPARE NOTEQUAL "${QT_QMAKE_EXECUTABLE_LAST}" "${QT_QMAKE_EXECUTABLE}" QT_QMAKE_CHANGED)
+  endif()
+  set(QT_QMAKE_EXECUTABLE_LAST "${QT_QMAKE_EXECUTABLE}" CACHE INTERNAL "" FORCE)
+
   _qt4_get_version_components("${QTVERSION}" QT_VERSION_MAJOR QT_VERSION_MINOR QT_VERSION_PATCH)
 
   # ask qmake for the mkspecs directory