In the protocol “An Efficient Method for Immortalizing Mouse Embryonic Fibroblasts by CRISPR-Mediated Deletion of the Tp53 Gene” (https://bio-protocol.org/e5159), published in Volume 15, Issue 2 of Bio-protocol, the electroporation solution used was incorrectly stated as TransIT-LT1 transfection reagent (Mirus Bio, catalog number: MIR 2304). The correct reagent is Ingenio Electroporation Solution (Mirus Bio, catalog number: MIR 50114). This information has now been corrected in the revised publication.