KiCAD / eeschema “Component Load Error”

I used the excellent Quick KICAD Library Component Builder recently to build a new component for eeschema in KiCAD, but when I imported the library, I got an error dialog that said, “Library component load error error <error <pin only had 6 parameters of the required 11 or 12> in DRAW command X> occurred at line 38 .” [sic] Line 38 was line after the pin definitions — the “ENDDRAW” line.

It turns out the exception was caused by a space in a pin name: I had typed “SER IN” as the name of the pin, where I should have used an underscore and typed “SER_IN”. The library utility doesn’t prohibit this, and KiCAD clearly doesn’t like it.