diff --git a/libavcodec/pcx.c b/libavcodec/pcx.c
index 568c150a35..5aa7b08462 100644
--- a/libavcodec/pcx.c
+++ b/libavcodec/pcx.c
@@ -42,7 +42,7 @@ static int pcx_init(AVCodecContext *avctx) {
 /**
  * @return advanced src pointer
  */
-static char *pcx_rle_decode(uint8_t *src, uint8_t *dst,
+static const char *pcx_rle_decode(const uint8_t *src, uint8_t *dst,
                             unsigned int bytes_per_scanline) {
     unsigned int i = 0;
     unsigned char run, value;
@@ -61,7 +61,7 @@ static char *pcx_rle_decode(uint8_t *src, uint8_t *dst,
     return src;
 }
 
-static void pcx_palette(uint8_t **src, uint32_t *dst, unsigned int pallen) {
+static void pcx_palette(const uint8_t **src, uint32_t *dst, unsigned int pallen) {
     unsigned int i;
 
     for (i=0; i<pallen; i++)
@@ -70,14 +70,15 @@ static void pcx_palette(uint8_t **src, uint32_t *dst, unsigned int pallen) {
 }
 
 static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
-                            uint8_t *buf, int buf_size) {
+                            const uint8_t *buf, int buf_size) {
     PCXContext * const s = avctx->priv_data;
     AVFrame *picture = data;
     AVFrame * const p = &s->picture;
     int xmin, ymin, xmax, ymax;
     unsigned int w, h, bits_per_pixel, bytes_per_line, nplanes, stride, y, x,
                  bytes_per_scanline;
-    uint8_t *ptr, *bufstart = buf;
+    uint8_t *ptr;
+    uint8_t const *bufstart = buf;
 
     if (buf[0] != 0x0a || buf[1] > 5 || buf[1] == 1 || buf[2] != 1) {
         av_log(avctx, AV_LOG_ERROR, "this is not PCX encoded data\n");
@@ -161,7 +162,7 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
 
     } else if (nplanes == 1 && bits_per_pixel == 8) {
         uint8_t scanline[bytes_per_scanline];
-        uint8_t *palstart = bufstart + buf_size - 769;
+        const uint8_t *palstart = bufstart + buf_size - 769;
 
         for (y=0; y<h; y++, ptr+=stride) {
             buf = pcx_rle_decode(buf, scanline, bytes_per_scanline);
@@ -213,7 +214,7 @@ static int pcx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     if (nplanes == 1 && bits_per_pixel == 8) {
         pcx_palette(&buf, (uint32_t *) p->data[1], 256);
     } else if (bits_per_pixel < 8) {
-        uint8_t *palette = bufstart+16;
+        const uint8_t *palette = bufstart+16;
         pcx_palette(&palette, (uint32_t *) p->data[1], 16);
     }