diff --git a/src/Design.cc b/src/Design.cc
index d6ae89d136..4670fb9a56 100644
--- a/src/Design.cc
+++ b/src/Design.cc
@@ -20,6 +20,7 @@
 #include "ord/OpenRoad.hh"
 #include "ord/Tech.h"
 #include "tcl.h"
+#include "tclDecls.h"
 #include "utl/Logger.h"
 
 namespace ord {
@@ -136,6 +137,7 @@ std::string Design::evalTclString(const std::string& cmd)
   ord::OpenRoad::setOpenRoad(openroad, /* reinit_ok */ true);
   Tcl_Interp* tcl_interp = openroad->tclInterp();
   sta::Sta::setSta(openroad->getSta());
+  Tcl_SetAssocData(tcl_interp, "design", nullptr, this);
   Tcl_Eval(tcl_interp, cmd.c_str());
   return std::string(Tcl_GetStringResult(tcl_interp));
 }