diff --git a/README b/README
index 9134910f4d..df4400f58b 100644
--- a/README
+++ b/README
@@ -20,6 +20,10 @@ FFmpeg README
 * The file libavcodec/i386/idct_mmx.c is distributed under the GNU General
   Public License. It is strictly an optimization and its use is optional.
 
+* The file libavcodec/ac3dec.c is distributed under the GNU General Public
+  License.  In order for (E-)AC-3 decoding to work you need to enable GPL
+ components.
+
 * The file libavdevice/x11grab.c is distributed under the GNU General
   Public License. X11 grabbing is optional.