--- multipath-tools-0.7.5/Makefile.inc
+++ multipath-tools-0.7.5/Makefile.inc
@@ -91,12 +91,13 @@
 		  -Wp,-D_FORTIFY_SOURCE=2 $(STACKPROT) \
 		  --param=ssp-buffer-size=4
 
-CFLAGS		:= $(OPTFLAGS) -DBIN_DIR=\"$(bindir)\" -DLIB_STRING=\"${LIB}\" -DRUN_DIR=\"${RUN}\" \
-		   -MMD -MP $(CFLAGS)
+CFLAGS		?= $(OPTFLAGS)
+CFLAGS		+= -DBIN_DIR=\"$(bindir)\" -DLIB_STRING=\"${LIB}\" -DRUN_DIR=\"${RUN}\" \
+		   -MMD -MP
 BIN_CFLAGS	= -fPIE -DPIE
 LIB_CFLAGS	= -fPIC
 SHARED_FLAGS	= -shared
-LDFLAGS		= -Wl,-z,relro -Wl,-z,now
+LDFLAGS		+= -Wl,-z,relro -Wl,-z,now
 BIN_LDFLAGS	= -pie
 
 # Check whether a function with name $1 has been declared in header file $2.
