diff --git a/libmultipath/Makefile b/libmultipath/Makefile
index 8a14b04..e5d5b10 100644
--- a/libmultipath/Makefile
+++ b/libmultipath/Makefile
@@ -6,7 +6,7 @@ BUILD = glibc
 
 include ../Makefile.inc
 
-CFLAGS = -I$(checkersdir)
+CFLAGS += -I$(checkersdir)
 
 OBJS = memory.o parser.o vector.o devmapper.o callout.o \
        hwtable.o blacklist.o util.o dmparser.o config.o \