diff --git a/src/Makefile.am b/src/Makefile.am
index ecd254e2..7806fa10 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -7,7 +7,7 @@ CFLAGS_O2 = $(CFLAGS_BASE) -O2
 CFLAGS_O3 = $(CFLAGS_BASE) -O3
 DEFAULT_INCLUDES=-I..
 
-AM_CFLAGS = $(CFLAGS_BASE)
+CFLAGS = $(CFLAGS_BASE)
 
 lib_LTLIBRARIES = libpostal.la
 libpostal_la_SOURCES = libpostal.c address_dictionary.c transliterate.c tokens.c trie.c trie_search.c string_utils.c file_utils.c numex.c utf8proc/utf8proc.c cmp/cmp.c geodb.c geo_disambiguation.c normalize.c bloom.c features.c geonames.c geohash/geohash.c unicode_scripts.c msgpack_utils.c