diff --git a/mkfile b/mkfile
index c31128f1..a446df4d 100644
--- a/mkfile
+++ b/mkfile
@@ -4,7 +4,7 @@ BIN=/$objtype/bin
 TARG=chibi-scheme
 MODDIR=/sys/lib/chibi-scheme
 
-CPPFLAGS= -Iinclude -DPLAN9 '-DSEXP_USE_STRING_STREAMS=0' '-DSEXP_USE_DEBUG=0' '-DSEXP_USE_DL=0' '-DSEXP_USE_GREEN_THREADS=0'
+CPPFLAGS= -Iinclude -DPLAN9 -DSEXP_USE_STRING_STREAMS=0 -DSEXP_USE_GREEN_THREADS=0
 CFLAGS= -p $CPPFLAGS
 
 OFILES=sexp.$O eval.$O main.$O