diff --git a/aegisub/libffms/Makefile.am b/aegisub/libffms/Makefile.am
index 05fb35557..851d4cea6 100644
--- a/aegisub/libffms/Makefile.am
+++ b/aegisub/libffms/Makefile.am
@@ -2,7 +2,7 @@ AUTOMAKE_OPTIONS = subdir-objects
 
 noinst_LIBRARIES = libffmpegsource_aegisub.a
 
-AM_CPPFLAGS = -Icore -Iinclude -D__UNIX__ -DFFMS_EXPORTS -DHAVE_STRLCPY @LIBAVFORMAT_CFLAGS@ @LIBAVCODEC_CFLAGS@ @LIBSWSCALE_CFLAGS@ @LIBAVUTIL_CFLAGS@ @LIBPOSTPROC_CFLAGS@ @BOOST_CPPFLAGS@
+AM_CPPFLAGS = -Icore -Iinclude -D__UNIX__ -DFFMS_EXPORTS -DHAVE_STRLCPY @LIBAVFORMAT_CFLAGS@ @LIBAVCODEC_CFLAGS@ @LIBSWSCALE_CFLAGS@ @LIBAVUTIL_CFLAGS@ @LIBPOSTPROC_CFLAGS@
 
 
 libffmpegsource_aegisub_a_SOURCES = \