diff --git a/Makefile b/Makefile
index 94d0b78..418b564 100644
--- a/Makefile
+++ b/Makefile
@@ -17,8 +17,7 @@ DESTDIR ?= dist
 PREFIX ?= /usr/local
 
 # normalized prefix
-PREFIX_N != (test -d $(PREFIX) && [ '-' != $(PREFIX) ] \
-	&& CDPATH= cd -P -- $(PREFIX) && pwd -P)
+PREFIX_N != dirname $(PREFIX)/.
 MANDIR != [ $(PREFIX_N) = / ] && printf '/usr/share/man\n' \
 	|| printf '/share/man\n'
 SYSEXITS != printf '\043include <sysexits.h>\n' | cpp -M - | tr ' ' '\n' \
@@ -26,7 +25,7 @@ SYSEXITS != printf '\043include <sysexits.h>\n' | cpp -M - | tr ' ' '\n' \
 
 CC ?= cc
 RUSTC ?= rustc
-RUSTLIBS = --extern getopt=build/o/libgetopt.rlib \
+RUSTFLAGS += --extern getopt=build/o/libgetopt.rlib \
 	--extern sysexits=build/o/libsysexits.rlib \
 	--extern strerror=build/o/libstrerror.rlib
 CFLAGS += -I$(SYSEXITS)
@@ -120,7 +119,7 @@ build/bin/mm: src/mm.rs build rustlibs
 .PHONY: npc
 npc: build/bin/npc
 build/bin/npc: src/npc.c build
-	$(CC) $(CFLAGAS) -o $@ src/npc.c
+	$(CC) $(CFLAGS) -o $@ src/npc.c
 
 .PHONY: rpn
 rpn: build/bin/rpn