diff --git a/qtcreator.pri b/qtcreator.pri
index 3e4a9490b38..f40eb12f2a1 100644
--- a/qtcreator.pri
+++ b/qtcreator.pri
@@ -170,8 +170,8 @@ INCLUDEPATH += \
     $$IDE_SOURCE_TREE/src/libs \
     $$IDE_SOURCE_TREE/tools
 
-QTC_PLUGIN_DIRS = $$(QTC_PLUGIN_DIRS)
-QTC_PLUGIN_DIRS = $$split(QTC_PLUGIN_DIRS, $$QMAKE_DIRLIST_SEP)
+QTC_PLUGIN_DIRS_FROM_ENVIRONMENT = $$(QTC_PLUGIN_DIRS)
+QTC_PLUGIN_DIRS += $$split(QTC_PLUGIN_DIRS_FROM_ENVIRONMENT, $$QMAKE_DIRLIST_SEP)
 QTC_PLUGIN_DIRS += $$IDE_SOURCE_TREE/src/plugins
 for(dir, QTC_PLUGIN_DIRS) {
     INCLUDEPATH += $$dir