diff --git a/src/plugins/projectexplorer/projecttree.cpp b/src/plugins/projectexplorer/projecttree.cpp
index fb865a768b5..24042850e6c 100644
--- a/src/plugins/projectexplorer/projecttree.cpp
+++ b/src/plugins/projectexplorer/projecttree.cpp
@@ -53,7 +53,9 @@ const char EXTERNAL_FILE_WARNING[] = "ExternalFile";
 }
 
 using namespace Utils;
-using namespace ProjectExplorer;
+
+namespace ProjectExplorer {
+
 using namespace Internal;
 
 ProjectTree *ProjectTree::s_instance = 0;
@@ -499,3 +501,5 @@ bool ProjectTree::isInNodeHierarchy(Node *n)
     } while (n);
     return false;
 }
+
+} // namespace ProjectExplorer