Connector with retainer projections integral with connector housing

A connector assembly comprising:

• a first housing having opposite front and rear ends and first and second cavities extending through the first housing from the front end to the rear end, a fit-on detection connector part between the cavities, first and second flexibility allowance spaces between the fit-on detection connector part and the respective first and second cavities, a first resiliently deformable lance between the first cavity and the first flexibility allowance space and a second resiliently deformable lance between the second cavity and the second flexibility allowance space, the lances being deformable into the respective flexibility allowance spaces;
• first terminal fittings in the respective cavities of the first housing and being locked by the respective lances, the first terminal fittings being removable from the cavities when the lances are deformed into the flexibility allowance spaces;
• and
• a second housing configured to fit together with the first housing along a fit-on direction, second terminal fittings mounted in the second housing and being connectable with the first terminal fittings when the housings are fit together, an interlocking connector mounted in the second housing between the second terminal fittings and being connectable with the fit-on detection connector part when the housings are fit together, first and second retainer projections unitary with the second housing and projecting in the fit-on direction, the retainer projections penetrating into the flexibility allowance spaces when the first and second housings are fit together properly for preventing the lances from flexing in an unlocking direction, wherein the fit-on detection connector part is sandwiched between the retainer projections when the first and second housings are fit together.