diff --git a/mod_fix.c b/mod_fix.c
index 6a431a4a5e7..7b5ab4418af 100644
--- a/mod_fix.c
+++ b/mod_fix.c
@@ -165,10 +165,20 @@ int fix_cmd(struct cmd_param *params, action_elem_t *elems)
 						goto error;
 					}
 				} else {
+					if (param->flags & CMD_PARAM_STATIC) {
+						LM_ERR("Param [%d] does not support formatted strings\n",i);
+						return E_CFG;
+					}
+
 					gp->pval = pve;
 					gp->type = GPARAM_TYPE_PVE;
 				}
 			} else if (elems[i].type == SCRIPTVAR_ST) {
+				if (param->flags & CMD_PARAM_STATIC) {
+					LM_ERR("Param [%d] does not support variables\n",i);
+					return E_CFG;
+				}
+
 				gp->pval = elems[i].u.data;
 				gp->type = GPARAM_TYPE_PVS;
 			} else {
diff --git a/sr_module.h b/sr_module.h
index 5e4232ef75d..a02b327e24e 100644
--- a/sr_module.h
+++ b/sr_module.h
@@ -118,6 +118,7 @@ typedef int (*mod_proc_wrapper)();
 #define CMD_PARAM_OPT        (1<<4)  /* optional parameter */
 #define CMD_PARAM_FIX_NULL   (1<<5)  /* run fixup even if optional parameter is omitted */
 #define CMD_PARAM_NO_EXPAND  (1<<6)  /* TMPHACK: do not pv-expand strings */
+#define CMD_PARAM_STATIC	 (1<<7)  /* don't accept variables or formatted string */
 
 struct cmd_param {
 	int flags;              /* parameter flags */