--- a/dpflib/Makefile
+++ b/dpflib/Makefile
@@ -10,7 +10,7 @@
 LIBS=-lusb -lsgutils2
 endif
 
-CFLAGS = -Wall -fPIC -I../include -g
+CFLAGS = -Wall -fPIC -I$(PREFIX)/include -I../include -g
 # CFLAGS += -DDEBUG
 
 ifndef DESTDIR