diff --git a/src/Base/Builder3D.cpp b/src/Base/Builder3D.cpp
index 8099268bee..3708b20741 100644
--- a/src/Base/Builder3D.cpp
+++ b/src/Base/Builder3D.cpp
@@ -124,13 +124,6 @@ const char* PolygonOffset::styleAsString() const
 
 // -----------------------------------------------------------------------------
 
-std::ostream& operator<<( std::ostream& os, Indentation m)
-{
-    for (int i = 0; i < m.count(); i++)
-        os << " ";
-    return os;
-}
-
 InventorOutput::InventorOutput(std::ostream& result, Indentation& indent)
   : result(result)
   , indent(indent)
diff --git a/src/Base/Builder3D.h b/src/Base/Builder3D.h
index 47f2b34c6f..bc7192fcab 100644
--- a/src/Base/Builder3D.h
+++ b/src/Base/Builder3D.h
@@ -159,6 +159,12 @@ public:
     int count() {
         return spaces;
     }
+    friend std::ostream& operator<<( std::ostream& os, Indentation m)
+    {
+        for (int i = 0; i < m.count(); i++)
+            os << " ";
+        return os;
+    }
 };
 
 class BaseExport InventorOutput