diff -up ffms2-5.0/configure.ac.orig ffms2-5.0/configure.ac
--- configure.ac.orig	2024-05-28 16:52:48.000000000 +0200
+++ configure.ac	2024-09-20 12:13:11.134979566 +0200
@@ -118,6 +118,10 @@ if test "$FFMPEG_WORKS" = no; then
 AC_MSG_FAILURE([cannot link with FFmpeg])
 fi
 
+PKG_CHECK_MODULES(VAPOURSYNTH, [vapoursynth])
+
+AC_SUBST([VAPOURSYNTH_CFLAGS])
+
 src_core_libffms2_la_LDFLAGS=""
 AC_MSG_CHECKING([whether -Wl,-Bsymbolic is needed])
 if test "$enable_shared" = yes; then
diff -up ffms2-5.0/Makefile.am.orig ffms2-5.0/Makefile.am
--- Makefile.am.orig	2024-09-20 12:12:14.272194649 +0200
+++ Makefile.am	2024-09-20 12:13:00.781018729 +0200
@@ -14,6 +14,7 @@ AM_CPPFLAGS = \
 	-DFFMS_EXPORTS \
 	-D__STDC_CONSTANT_MACROS \
 	@FFMPEG_CFLAGS@ \
+	@VAPOURSYNTH_CFLAGS@ \
 	@ZLIB_CPPFLAGS@ \
 	-include config.h
 AM_CXXFLAGS = -fvisibility=hidden
@@ -39,8 +40,6 @@ src_core_libffms2_la_SOURCES = \
 	src/core/videoutils.h \
 	src/core/zipfile.cpp \
 	src/core/zipfile.h \
-	src/vapoursynth/VapourSynth4.h \
-	src/vapoursynth/VSHelper4.h \
 	src/vapoursynth/vapoursource4.cpp \
 	src/vapoursynth/vapoursource4.h \
 	src/vapoursynth/vapoursynth4.cpp