--- a/debian/rules	2019-10-08 15:32:45.676295877 -0700
--- b/debian/rules	2019-10-08 15:44:01.846221833 -0700
@@ -3,7 +3,7 @@
 export DH_ALWAYS_EXCLUDE=.svn
 
 LDFLAGS=-Wl,-z,defs -Wl,--as-needed -Wl,--no-undefined
-CFLAGS=-std=gnu89
+CFLAGS=-std=gnu89 $(shell dpkg-buildflags --get CFLAGS)
 
 config: config-stamp
 config-stamp: