diff --git a/custom-ports/ffmpeg/portfile.cmake b/custom-ports/ffmpeg/portfile.cmake
index 33aad01a..b2db8637 100644
--- a/custom-ports/ffmpeg/portfile.cmake
+++ b/custom-ports/ffmpeg/portfile.cmake
@@ -77,7 +77,8 @@ elseif(VCPKG_TARGET_IS_EMSCRIPTEN)
          --enable-encoder=aac*
          --enable-decoder=aac*
          --enable-protocol=file
-         --enable-demuxer=mov
+         --enable-demuxer=mov,mp4
+         --enable-muxer=mov,mp4
          --nm=emnm
          --ar=emar
          --ranlib=emranlib