It's due to CamInternalAddons.h generated header and included by src/add-ons/media/media-add-ons/usb_webcam/CamRoster.cpp at lines 17 and 133. It seems the src/add-ons/media/media-add-ons/usb_webcam/Jamfile's USBWebcamHeaderGen rule don't run again when the sources list (but not their content) changes, like when the UVC add-on was disabled.in r36740. Anyway. Stephan is right, "jam clean" works fine, and is far easier than removing generated/.../usb_webcam/CamInternalAddOns.h file himself. Maybe one solution would be to always generate those headers : ALWAYS [ FGristFiles CamInternalAddons.h ] ; ALWAYS [ FGristFiles CamInternalSensors.h ] ; ALWAYS [ FGristFiles CamInternalColorSpaceTransforms.h ] ; Bye, Philippe.