There is an error in the code I added to initialisation routine of Z8E version 3. It only affects users wanting to patch the breakpoint vector address to something other than 38h. To fix it in the source code, delete the three consecutive RRCA instructions near the beginning of routine ninit: and change the following OR 0F8h instruction to OR 0C7h. To fix the object code without reassembling, use the faulty Z8E to patch itself. z8e z8e.com< *e 15f< 015F 0F 0< 0160 0F 0< 0161 0F 0< 0162 F6 < 0163 F8 C7< 0164 xx . *w z8e.com< *g 0< This patch will be included in the next release of the program.