--- a/Makefile.in
+++ b/Makefile.in
@@ -20,10 +20,7 @@
 
 # We may have separate source and binary trees -- make sure we can find
 # dxpcconf.h
-CPPFLAGS = -I.
-
-.C.o:
-	$(CXX) $(CPPFLAGS) -c $(CXXFLAGS) $<
+CPPFLAGS += -I.
 
 TARGET=	dxpc$(EXEEXT)
 
@@ -53,18 +50,18 @@
 OBJS=	$(SRCS:.C=.o)
 
 $(TARGET):	$(OBJS)
-	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -o $@ $(OBJS) $(LDFLAGS) $(LIBS)
+	$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
 
 ifeq ($(MINGW32),true)
 $(SECONDTARGET): $(OBJS)
-	$(CXX) -mwindows $(CPPFLAGS) $(CXXFLAGS) -o $@ $(OBJS) $(LDFLAGS) $(LIBS)
+	$(CXX) -mwindows $(CXXFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
 endif
 
 pure_$(TARGET):	$(OBJS)
-	purify $(CXX) $(CPPFLAGS) $(CXXFLAGS) -o $@ $(OBJS) $(LDFLAGS) $(LIBS)
+	purify $(CXX) $(CXXFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
 
 quant_$(TARGET):	$(OBJS) $(OBJS)
-	quantify $(CXX) $(CPPFLAGS) $(CXXFLAGS) -o $@ $(OBJS) $(LDFLAGS) $(LIBS)
+	quantify $(CXX) $(CXXFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
 
 depends:
 	makedepend -f Makefile $(SRCS)
@@ -72,12 +69,12 @@
 install: install.bin install.man
 
 install.bin:	$(TARGET)
-	$(srcdir)/mkinstalldirs $(bindir)
-	$(INSTALL) $(TARGET) $(bindir)/$(TARGET)
+	$(srcdir)/mkinstalldirs $(DESTDIR)$(bindir)
+	$(INSTALL) $(TARGET) $(DESTDIR)$(bindir)/$(TARGET)
 
 install.man:
-	$(srcdir)/mkinstalldirs $(man1dir)
-	$(INSTALL_DATA) $(TARGET).man $(man1dir)/$(TARGET).1
+	$(srcdir)/mkinstalldirs $(DESTDIR)$(man1dir)
+	$(INSTALL_DATA) $(TARGET).man $(DESTDIR)$(man1dir)/$(TARGET).1
 
 clean:
 	-rm -f *~ *.o $(TARGET) pure_* quant_* *.bak core gmon.out