Error compiling 1.9.1 on Mac OS X

When making ruby-1.9.1-p0 on Mac OS X (10.5.6), I get the following
error:

cc -dynamic -bundle -undefined suppress -flat_namespace -o .ext/i386-
darwin9/enc/trans/transdb.bundle enc/trans/transdb.o -L. -L. -L. -L/
opt/local/lib -L/usr/local/lib -lruby1.9 -lpthread -ldl -lobjc
ld: in /usr/local/lib/libstdc++.6.dylib, file is not of required
architecture
collect2: ld returned 1 exit status
make[1]: *** [.ext/i386-darwin9/enc/trans/transdb.bundle] Error 1
make: *** [trans] Error 2

Ideas?