This causes serious breakage for me: Searching for, say, a word containing an ß ("eszet"), crashes: (gdb) bt #0 0x9003d66c in kill () #1 0x9010e8cf in raise () #2 0x9010d422 in abort () #3 0x00060660 in really_abort () at emacs.c:4693 #4 0x0005ed64 in assert_failed (file=0x29eb40 "search.c", line=1746, expr=0x29eff8 "charset_base == (untranslated & ~ICHAR_FIELD3_MASK)") at emacs.c:3987 #5 0x001ca6c6 in boyer_moore (buf=0x20d5c00, base_pat=0xbfffa6b0 "fleiß", len=6, pos=289, lim=395, n=1, trt=4644940, inverse_trt=4643748, charset_base=0) at search.c:1746 #6 0x001c99bb in search_buffer (buf=0x20d5c00, string=33883876, charbpos=289, buflim=395, n=1, RE=0, trt=4644940, inverse_trt=4643748, posix=0) at search.c:1457 #7 0x001c8bc0 in search_command (string=33883876, limit=3148476, noerror=3147204, count=3148476, buffer=3148476, direction=1, RE=0, posix=0) at search.c:1155 #8 0x001cb9f4 in Fsearch_forward (string=33883876, limit=3148476, noerror=3147204, count=3148476, buffer=3148476) at search.c:2252 Aidan, could you look into this?