
10 S.W.3d 788 (2000)
Patrick Keith WILLIAMS, Appellant,
v.
The STATE of Texas, Appellee.
No. 10-98-139-CR.
Court of Appeals of Texas, Waco.
January 26, 2000.
Kathryn J. Gilliam, Beard & Kultgen, Waco, for appellant.
*789 John W. Segrest, Criminal Dist. Atty., Waco, for appellee.
Before Chief Justice DAVIS, Justice VANCE, Justice GRAY.

OPINION
REX D. DAVIS, Chief Justice.
Appellant Patrick Keith Williams pleaded guilty before a jury to aggravated assault, and the jury assessed punishment at twelve years' confinement in the Texas Department of Criminal JusticeInstitutional Division. See TEX. PEN.CODE ANN. § 22.02(a)(2) (Vernon 1994). Williams's sole issue on appeal claims that the trial court erred when it failed to sua sponte withdraw his guilty plea after the testimony allegedly raised an issue concerning his innocence.
If a defendant enters a plea of guilty before a jury and evidence is introduced which "reasonably and fairly raises [an] issue" concerning his innocence, the trial court has a duty to sua sponte withdraw the defendant's guilty plea and enter a not guilty plea. Holland v. State, 761 S.W.2d 307, 322 (Tex.Crim.App.1988); Griffin v. State, 703 S.W.2d 193, 195 (Tex. Crim.App.1986) (op. on reh'g); Hoffman v. State, 922 S.W.2d 663, 673 (Tex.App.-Waco 1996, pet. ref'd).
This rule is a vital safeguard which operates to protect the accused from any outside pressure which could result in an innocent party being convicted, upon his own plea of guilty, of a crime he did not commit .... [and] to assure the voluntary nature of the plea.
Griffin, 703 S.W.2d at 195.
The Court of Criminal Appeals has recently held that, "[e]xcept for complaints involving fundamental constitutional systemic requirements ..., all other complaints... are waived by failure to comply with Rule 33.1." Ibarra v. State, 11 S.W.3d 189, 197 (Tex.Crim.App. 1999). The United States Supreme Court has classified these "fundamental" requirements "as those which, when denied, `defy analysis by "harmless error" standards.'" Foster v. State, 8 S.W.3d 445, 446 (Tex. App.-Waco 1999, no pet. h.) (quoting Arizona v. Fulminante, 499 U.S. 279, 309, 111 S.Ct. 1246, 1265, 113 L.Ed.2d 302 (1991)).
A question concerning the voluntariness of a guilty plea does not fall within the definition of such "fundamental" requirements. See Cain v. State, 947 S.W.2d 262, 264 (Tex.Crim.App.1997). In Cain, the Court wrote:
Except for certain federal constitutional errors labeled by the United States Supreme Court as "structural," no error, whether it relates to jurisdiction, voluntariness of a plea, or any other mandatory requirement, is categorically immune to a harmless error analysis.
Id. (emphasis added). Because a challenge to the voluntariness of a guilty plea does not implicate one of the "fundamental" requirements identified by the Supreme Court, an appellant must properly preserve such a complaint for appellate review. See Foster, at 447; see also Ibarra, slip op. at 197.
Williams's sole complaint on appeal relates to the voluntariness of his guilty plea. Griffin, 703 S.W.2d at 195. Thus, it must be properly preserved for appellate review in accordance with Rule 33.1. See Foster, at 447; see also Ibarra, slip op. at 197. Williams failed to preserve this issue by objection, request, or in a timely presented motion for new trial. See TEX.R.App. P. 33.1(a)(1)(A). Accordingly, we overrule his sole issue.
We affirm the judgment.
