--- a/netwerk/mime/nsMimeTypes.h
+++ b/netwerk/mime/nsMimeTypes.h
@@ -82,16 +82,17 @@
 #define AUDIO_MP3                           "audio/mpeg"
 #define AUDIO_MP4                           "audio/mp4"
 #define AUDIO_AMR                           "audio/amr"
 #define AUDIO_FLAC                          "audio/flac"
 #define AUDIO_3GPP                          "audio/3gpp"
 #define AUDIO_3GPP2                         "audio/3gpp2"
 #define AUDIO_MIDI                          "audio/x-midi"
 #define AUDIO_MATROSKA                      "audio/x-matroska"
+#define AUDIO_FLAC                          "audio/flac"
 
 #define BINARY_OCTET_STREAM                 "binary/octet-stream"
 
 #define IMAGE_GIF                           "image/gif"
 #define IMAGE_JPEG                          "image/jpeg"
 #define IMAGE_JPG                           "image/jpg"
 #define IMAGE_PJPEG                         "image/pjpeg"
 #define IMAGE_PNG                           "image/png"

--- a/toolkit/components/mediasniffer/nsMediaSniffer.cpp
+++ b/toolkit/components/mediasniffer/nsMediaSniffer.cpp
@@ -28,17 +28,19 @@ static const uint32_t MAX_BYTES_SNIFFED_
 NS_IMPL_ISUPPORTS(nsMediaSniffer, nsIContentSniffer)
 
 nsMediaSnifferEntry nsMediaSniffer::sSnifferEntries[] = {
   // The string OggS, followed by the null byte.
   PATTERN_ENTRY("\xFF\xFF\xFF\xFF\xFF", "OggS", APPLICATION_OGG),
   // The string RIFF, followed by four bytes, followed by the string WAVE
   PATTERN_ENTRY("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF", "RIFF\x00\x00\x00\x00WAVE", AUDIO_WAV),
   // mp3 with ID3 tags, the string "ID3".
-  PATTERN_ENTRY("\xFF\xFF\xFF", "ID3", AUDIO_MP3)
+  PATTERN_ENTRY("\xFF\xFF\xFF", "ID3", AUDIO_MP3),
+  // FLAC with standard header
+  PATTERN_ENTRY("\xFF\xFF\xFF\xFF", "fLaC", AUDIO_FLAC)
 };
 
 // For a complete list of file types, see http://www.ftyps.com/index.html
 nsMediaSnifferEntry sFtypEntries[] = {
   PATTERN_ENTRY("\xFF\xFF\xFF", "mp4", VIDEO_MP4), // Could be mp41 or mp42.
   PATTERN_ENTRY("\xFF\xFF\xFF", "avc", VIDEO_MP4), // Could be avc1, avc2, ...
   PATTERN_ENTRY("\xFF\xFF\xFF", "3gp", VIDEO_3GPP), // Could be 3gp4, 3gp5, ...
   PATTERN_ENTRY("\xFF\xFF\xFF\xFF", "M4A ", AUDIO_MP4),