diff --git a/configure b/configure
index cc23506801..80f486b4b4 100755
--- a/configure
+++ b/configure
@@ -1561,8 +1561,8 @@ _libavcodec=auto
 _amr_nb=auto
 _amr_nb_fixed=auto
 _amr_wb=auto
-_libavdecoders=`grep 'register_avcodec(&[a-z]_decoder)' libavcodec/allcodecs.c  | sed 's/.*&\(.*\)).*/\1/'`
-_libavencoders=`grep 'register_avcodec(&[a-z]_encoder)' libavcodec/allcodecs.c  | sed 's/.*&\(.*\)).*/\1/'`
+_libavdecoders=`grep 'register_avcodec(&[a-z0-9_]*_decoder)' libavcodec/allcodecs.c  | sed 's/.*&\(.*\)).*/\1/'`
+_libavencoders=`grep 'register_avcodec(&[a-z0-9_]*_encoder)' libavcodec/allcodecs.c  | sed 's/.*&\(.*\)).*/\1/'`
 _libavparsers=`grep 'av_register_codec_parser(&[a-z]' libavcodec/allcodecs.c  | sed 's/.*&\(.*\)).*/\1/'`
 _libavdemuxers=`grep 'av_register_input_format(&[a-z]' libavformat/allformats.c  | sed 's/.*&\(.*\)).*/\1/'`
 _libavmuxers=`grep 'av_register_output_format(&[a-z]' libavformat/allformats.c  | sed 's/.*&\(.*\)).*/\1/'`