OPINION
HARTEN, JudgeA representative of the Commissioner of Economic Security reviewed sua sponte and reversed the decision of a reemployment insurance judge that relator did not commit misconduct and was therefore entitled to reemployment insurance benefits. Because we hold that relator did commit misconduct within the meaning of Minn.Stat. § 268.095, subd. 6 (1998), we affirm.
FACTS
Relator Abdulahi Isse was employed by respondent Alamo Rent-a-Car, Inc., to clean cars. In January 1998, while relator was on an office phone making a medical appointment for his wife, a co-worker approached relator and asked him to return to work because there were cars to clean. Relator responded with an obscenity. After relator finished the phone call, he and the co-worker began arguing. An altercation ensued; relator grabbed the co-worker by the shirt and pushed him against a wall. A third employee separated them. Prior to this incident, there had been no problems with relator’s employment. Relator was suspended and later dis*139charged for grabbing and pushing the coworker.
Relator then sought reemployment insurance benefits. A Department of Economic Security claims representative held that relator had been discharged for reasons other than misconduct and was entitled to benefits. The employer appealed, and a reemployment insurance judge affirmed, relying on Hamilton v. International Dairy Queen, Inc. 346 N.W.2d 138 (Minn.1984), and Oman v. Daig Corp., 375 N.W.2d 533 (Minn.App.1985), to hold that neither an isolated use of strong language nor an isolated confrontation with another employee constitutes misconduct.
Hamilton relies on a contemporaneously filed decision, Windsperger v. Broadway Liquor Outlet, 346 N.W.2d 142 (Minn.1984), which quoted the definition of misconduct adopted in Tilseth v. Midwest Lumber Co., 295 Minn. 372, 204 N.W.2d 644 (1973). That definition excludes from misconduct “inad-vertencies or ordinary negligence in isolated instances.” Windsperger, 346 N.W.2d at 144 (quoting Tilseth, 295 Minn. at 374, 375, 204 N.W.2d at 646). Windsperger holds “that an isolated hotheaded incident which does not interfere with the employer’s business is not misconduct * * * justifying a denial of unemployment compensation benefits.” Id. at 145. Oman reiterates the holding:
Applying the Tilseth standard, the supreme court [in Windsperger ] has also held that “an isolated hotheaded incident which does not interfere with the employer’s business is not misconduct * * * justifying a denial of unemployment compensation benefits.”
375 N.W.2d at 536 (quoting Windsperger, 346 N.W.2d at 145).
The reemployment insurance judge’s decision was reviewed sua sponte by a commissioner’s representative, who reversed on the ground that the new statutory definition of misconduct effective July 1, 1997, did not exclude from misconduct isolated outbursts such as relator’s. Relator appeals from the denial of benefits.
ISSUE
Is an isolated workplace outburst during which an employee angrily grabs and pushes a co-worker misconduct within the meaning of Minn.Stat. § 268.095, subd. 6 (1998)?
ANALYSIS
The determination that an employee committed misconduct is a mixed question of fact and law. A reviewing court will affirm if the findings of fact are “not without support in the evidence” and if the conclusion on those facts is not contrary to the statutory mandate. Colburn v. Pine Portage Madden Bros., 346 N.W.2d 159, 161 (Minn.1984).
The commissioner’s representative based the findings that relator uttered an obscenity and grabbed and pushed a co-worker on the testimony of an employee who witnessed the altercation and the statement of the employee who separated relator and the co-worker, noting that both sources were persuasive. The commissioner’s representative’s findings are manifestly not without support in the evidence and must be affirmed.
Nor is the conclusion on those facts contrary to the statutory mandate. The conclusion is based on Minn.Stat. § 268.095, subd. 6 (1998):
Misconduct is intentional conduct showing a disregard of:
(1) the employer’s interest;
(2) the standards of behavior that an employer has the right to expect of the employee; or
(3) the employee’s duties and obligations to the employer.
The commissioner’s representative found that grabbing and shoving another employee “unquestionably violates the standard of behavior the employer had a right to expect of [relator].”
The recently enacted statutory definition of misconduct closely resembles the common-law definition adopted in Tilseth, 295 Minn. 372, 204 N.W.2d 644 (1973). The statute, however, excludes from misconduct only “inefficiency, inadvertence, simple unsatisfactory conduct, or poor performance as a result of inability or incapacity.” Minn.Stat. § 268.095, subd. 6. Tilseth excluded “mere *140inefficiency, unsatisfactory conduct, failure in good performance as the result of inability or incapacity, inadvertencies or ordinary negligence in isolated instances * * 295 Minn. at 374-75, 204 N.W.2d at 646, and this “isolated instances” language was the basis for the holding that “an isolated hotheaded incident which does not interfere with the employer’s business is not misconduct * * *.” Windsperger, 346 N.W.2d at 145.1
We are not free to supply an “isolated instances” exception to the statutory definition of misconduct.
[W]hen a statutory question involves the failure of expression rather than the ambiguity of expression, this court is not free to substitute amendment for construction and thereby supply the omissions of the legislature. * * * Moreover, this court is prohibited from adding words to a statute and cannot supply what the legislature either purposely omitted or inadvertently overlooked.
Tracy State Bank v. Tracy-Garvin Coop., 573 N.W.2d 393, 395 (Minn.App.1998) (citations omitted). Because the phrase the legislature omitted was the basis for considering “hotheaded incidents” as an exception to misconduct, that exception is no longer Minnesota law.2
DECISION
The commissioner’s representative correctly concluded that relator’s conduct fell within the statutory definition of misconduct, i.e., disregard of “the standards of behavior that an employer has the right to expect of the employee,” and that relator was not entitled to benefits.
Affirmed.
. See also McCoy v. Spicer Off-Highway Axle Div., 412 N.W.2d 24, 27 (Minn.App.1987) (throwing hammer at the floor during dispute with supervisor did not disqualify); Norman v. Rosemount, Inc. 383 N.W.2d 443, 444 (Minn.App.1986) (throwing crumpled piece of paper at supervisor and walking away did not disqualify) review denied (Minn. May 22, 1986); Oman, 375 N.W.2d at 535 (isolated confrontation in which claimant threw a small plastic object at co-worker, pushed co-worker’s chair and pulled co-worker’s cap did not disqualify). But see McGowan v. Executive Express Transp. Enters., 420 N.W.2d 592, 595 (Minn.1988) ("We believe that [Windsperger] reachfes] into the outer limits of eligibility. We decline to liberalize further the granting of benefits contained in [it.]”)
. We note that caselaw interpreting those elements of the Tilseth definition that are reflected in the statute remains good law.