Gas formation or gassy defect in aging cheese continues to be a concern in the dairy industry. This defect is manifest by slits or cracks in the cheese body and/or “blown wrappers” in cheeses aged longer than 3 mo, and tends to be sporadic and recurrent. These slits, cracks, and voids are not usually evident until cheese is graded unless cheese packaging becomes loose. Over the years, a long list of microbial culprits has been assembled, but with limited evidence concerning their continuing role in causing gassy defect. In Cheddar cheese, nonstarter lactic acid bacteria (NSLAB) populate the cheese in the latter stages of ripening, and are sometimes associated with undesirable flavors and textures, including gas production. Because enumeration and identification of NSLAB has generally been restricted to species forming easily observed colonies within 2 d at 30 or 37°C on MRS, slow growing lactobacilli species have been overlooked in past attempts to identify the cause of gas and textural defects in aging cheese. A new Lactobacillus species, Lactobacillus wasatchensis, was recently isolated using prolonged low temperature incubation from a sample of gas-blown Cheddar cheese. Genomic analysis, metabolic characterization, cheese trials, and survey data strongly indicates this organism is a primary cause of late gas defect. Recent studies have also shown several other Lactobacillus species to produce gas in culture studies and experimental cheese batches, especially under specific conditions. The presence of Lb. wasatchensis, and other lactobacilli, in commercial Cheddar cheese could mean the possibility of cheese becoming blown or split during aging, resulting in downgraded cheese. Strategies for detecting and enumerating Lb. wasatchensis, and other gas-producing LAB, along with best practices to decrease late gassy defect in aging cheese will be discussed.