diff --git a/modules/codec/stl.c b/modules/codec/stl.c
index 3f3ae7a939a3d2c09b2e2cb5ee9c686fdce5d6c7..a00e0290a1147f208866d4b8f601815c934f3788 100644
--- a/modules/codec/stl.c
+++ b/modules/codec/stl.c
@@ -434,7 +434,7 @@ static int Decode(decoder_t *p_dec, block_t *p_block)
     return VLCDEC_SUCCESS;
 }
 
-static int ParseGSI(const decoder_t *dec, decoder_sys_t *p_sys)
+static int ParseGSI(decoder_t *dec, decoder_sys_t *p_sys)
 {
     uint8_t *header = dec->fmt_in.p_extra;
     if (!header) {