diff --git a/DDCore/src/LCDDImp.h b/DDCore/src/LCDDImp.h
index 6b682347c8f358c1ff0b28b75a230a154962ca9e..416f93111e3cd7c65116a937e80f6f5373ff15b5 100644
--- a/DDCore/src/LCDDImp.h
+++ b/DDCore/src/LCDDImp.h
@@ -108,11 +108,11 @@ namespace DD4hep {
       }
       /// Return handle to material describing air
       virtual Material air() const {
-        return m_materialVacuum;
+        return m_materialAir;
       }
       /// Return handle to material describing vacuum
       virtual Material vacuum() const {
-        return m_materialAir;
+        return m_materialVacuum;
       }
       /// Return handle to "invisible" visualization attributes
       virtual VisAttr invisible() const {