diff --git a/core/metacling/src/TCling.cxx b/core/metacling/src/TCling.cxx
index d5cb7b1745f2d..8d657a4bb54bd 100644
--- a/core/metacling/src/TCling.cxx
+++ b/core/metacling/src/TCling.cxx
@@ -1323,7 +1323,6 @@ static void RegisterPreIncludedHeaders(cling::Interpreter &clingInterp)
 #ifndef R__WIN32
    PreIncludes += "#include <cassert>\n";
 #endif
-   PreIncludes += "using namespace std;\n";
    clingInterp.declare(PreIncludes);
 }