diff --git a/variables.c b/variables.c
index 2e8b38c..8cd5f58 100644
--- a/variables.c
+++ b/variables.c
@@ -1766,7 +1766,7 @@ initialize_dynamic_variables ()
   INIT_DYNAMIC_VAR ("LINENO", (char *)NULL, get_lineno, assign_lineno);
   VSETATTR (v, att_integer);
 
-  INIT_DYNAMIC_VAR ("BASHPID", (char *)NULL, get_bashpid, null_assign);
+  INIT_DYNAMIC_VAR ("BASHPID", (char *)NULL, get_bashpid, (sh_var_assign_func_t *)NULL);
   VSETATTR (v, att_integer|att_readonly);
 
 #if defined (HISTORY)