diff --git a/library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Sniffer.java b/library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Sniffer.java
index 00acb29906..72ce336b73 100644
--- a/library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Sniffer.java
+++ b/library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Sniffer.java
@@ -37,6 +37,7 @@ import java.io.IOException;
         0x69736f34, // iso4
         0x69736f35, // iso5
         0x69736f36, // iso6
+        0x69736f39, // iso9
         0x61766331, // avc1
         0x68766331, // hvc1
         0x68657631, // hev1