diff --git a/libavcodec/pictordec.c b/libavcodec/pictordec.c
index 2dbc040b5c..8b075bfd0c 100644
--- a/libavcodec/pictordec.c
+++ b/libavcodec/pictordec.c
@@ -62,7 +62,7 @@ static void picmemset(PicContext *s, AVFrame *frame, unsigned value, int run,
 {
     uint8_t *d;
     int shift = *plane * bits_per_plane;
-    int mask  = ((1 << bits_per_plane) - 1) << shift;
+    unsigned mask  = ((1 << bits_per_plane) - 1) << shift;
     value   <<= shift;
 
     while (run > 0) {