diff --git a/apps/app_voicemail.c b/apps/app_voicemail.c
index 90e0795b7268f08f034e585909c5bd01454f7ba5..1e679965983ea578678d220eff2f79aeb56ff3b5 100644
--- a/apps/app_voicemail.c
+++ b/apps/app_voicemail.c
@@ -3676,8 +3676,8 @@ static void prep_email_sub_vars(struct ast_channel *ast, struct ast_vm_user *vmu
 	pbx_builtin_setvar_helper(ast, "VM_CONTEXT", context);
 	pbx_builtin_setvar_helper(ast, "VM_MAILBOX", mailbox);
 	pbx_builtin_setvar_helper(ast, "VM_CALLERID", ast_callerid_merge(callerid, sizeof(callerid), cidname, cidnum, "Unknown Caller"));
-	pbx_builtin_setvar_helper(ast, "VM_CIDNAME", (cidname ? cidname : "an unknown caller"));
-	pbx_builtin_setvar_helper(ast, "VM_CIDNUM", (cidnum ? cidnum : "an unknown caller"));
+	pbx_builtin_setvar_helper(ast, "VM_CIDNAME", (!ast_strlen_zero(cidname) ? cidname : "an unknown caller"));
+	pbx_builtin_setvar_helper(ast, "VM_CIDNUM", (!ast_strlen_zero(cidnum) ? cidnum : "an unknown caller"));
 	pbx_builtin_setvar_helper(ast, "VM_DATE", date);
 	pbx_builtin_setvar_helper(ast, "VM_CATEGORY", category ? ast_strdupa(category) : "no category");
 	pbx_builtin_setvar_helper(ast, "VM_FLAG", flag);