diff --git a/cde/programs/dtpad/dtpad.c b/cde/programs/dtpad/dtpad.c
index eba15a972..b5303cf0c 100644
--- a/cde/programs/dtpad/dtpad.c
+++ b/cde/programs/dtpad/dtpad.c
@@ -1107,7 +1107,7 @@ SetWorkSpaceHints(
     {
       ptr = MbStrchr (workspaces, ' ');
 
-      if (ptr != NULL) *ptr = NULL;
+      if (ptr != NULL) *ptr = 0;
 
       workspace_atoms = (Atom *) XtRealloc ((char *)workspace_atoms,
                         sizeof (Atom) * (num_workspaces + 1));