ruby/trunk rev 16276 broken? ib/erb.rb:429:in `initialize': wrong argument type StringScanner (expected true) (TypeError)

Build crashes shortly after miniruby linkage

...
gcc -g -O2   -L.  -rdynamic -Wl,-export-dynamic   main.o dln.o
dmyencoding.o miniprelude.o array.o bignum.o class.o compar.o complex.o
dir.o enum.o enumerator.o error.o eval.o load.o proc.o file.o gc.o
hash.o inits.o io.o marshal.o math.o numeric.o object.o pack.o parse.o
process.o prec.o random.o range.o rational.o re.o regcomp.o regenc.o
regerror.o regexec.o regparse.o regsyntax.o ruby.o signal.o sprintf.o
st.o string.o struct.o time.o transcode.o util.o variable.o version.o
blockinlining.o compile.o debug.o iseq.o vm.o vm_dump.o thread.o cont.o
id.o ascii.o us_ascii.o unicode.o utf_8.o strlcpy.o strlcat.o  dmyext.o
 -lpthread -lrt -ldl -lcrypt -lm   -o miniruby
rm -f ruby
ruby -Ks ./tool/insns2vm.rb --srcdir="." opt_sc.inc
rm -f ruby
ruby -Ks ./tool/insns2vm.rb --srcdir="." optunifs.inc
./miniruby -I./lib  ./enc/make_encdb.rb ./enc encdb.h.new
./tool/ifchange "encdb.h" "encdb.h.new"
encdb.h updated
./miniruby -I./lib  ./enc/trans/make_transdb.rb ./enc/trans transdb.h.new
./tool/ifchange "transdb.h" "transdb.h.new"
transdb.h updated
rbconfig.rb updated
gcc -g -O2   -I. -I.ext/include/i686-linux -I./include -I.
-DRUBY_EXPORT   -o encoding.o -c encoding.c
./miniruby -I./lib  -I. -rrbconfig ./tool/compile_prelude.rb \
		./prelude.rb ./enc/prelude.rb ./gem_prelude.rb prelude.c.new
/home/stephens/local/src/ruby-trunk/lib/erb.rb:429:in `initialize':
wrong argument type StringScanner (expected true) (TypeError)
	from /home/stephens/local/src/ruby-trunk/lib/erb.rb:429:in `new'
	from /home/stephens/local/src/ruby-trunk/lib/erb.rb:429:in `scan'
	from /home/stephens/local/src/ruby-trunk/lib/erb.rb:524:in `compile'
	from /home/stephens/local/src/ruby-trunk/lib/erb.rb:691:in `initialize'
	from ./tool/compile_prelude.rb:62:in `new'
	from ./tool/compile_prelude.rb:62:in `<main>'
make: *** [prelude.c] Error 1