Sen. Ted Cruz (R-TX) told NBC News on Monday that it was “inappropriate” for presumptive GOP nominee Donald Trump to attack a federal judge’s ethnicity.

“It’s inappropriate to be attacking a federal judge’s race or ethnicity,” Cruz told NBC News. “You’re going to have to ask Donald to explain the reason he says the things he does. I’m not going to try to do so.”

Trump had said that U.S. District Judge Gonzalo Curiel, who is presiding over cases against Trump University in California, has a conflict of interest because of his “Mexican heritage.” The businessman has railed against Hispanics since he launched his campaign, when he infamously stated that some undocumented immigrants were “rapists” and “criminals.”

Cruz has dodged answering whether he would support Trump as the Republican nominee after he dropped his own bid for the White House.