--- a/generic/dpCmds.c	2017-03-24 11:39:24.636119960 +0000
+++ b/generic/dpCmds.c	2017-03-24 11:33:00.387609539 +0000
@@ -11,6 +11,7 @@
  *
  */
 
+#define USE_INTERP_RESULT 1
 #include <tclInt.h>
 #include "generic/dpInt.h"
  
diff -ru tcl-dp-4.0b2/generic/dpFilters.c tcl-dp-4.0b2-new/generic/dpFilters.c
--- tcl-dp-4.0b2/generic/dpFilters.c	2017-03-24 11:28:55.000000000 +0000
+++ tcl-dp-4.0b2-new/generic/dpFilters.c	2017-03-24 11:37:25.713652494 +0000
@@ -1,3 +1,4 @@
+#define USE_INTERP_RESULT 1
 #include "generic/dp.h"
 #include <errno.h>
 #include <string.h>
diff -ru tcl-dp-4.0b2/generic/dpRPC.c tcl-dp-4.0b2-new/generic/dpRPC.c
--- tcl-dp-4.0b2/generic/dpRPC.c	2017-03-24 11:39:24.636119960 +0000
+++ tcl-dp-4.0b2-new/generic/dpRPC.c	2017-03-24 11:36:44.096488904 +0000
@@ -91,6 +91,7 @@
  *	will be reclaimed.
  */
 
+#define USE_INTERP_RESULT 1
 #include <tclInt.h>
 #include "generic/dpInt.h"