diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 2481959a21..1ba8074272 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -892,7 +892,7 @@ static int pxr24_uncompress(EXRContext *s, const uint8_t *src,
                 in     = ptr[3] + s->xdelta;
 
                 for (j = 0; j < s->xdelta; ++j) {
-                    uint32_t diff = (*(ptr[0]++) << 24) |
+                    uint32_t diff = ((uint32_t)*(ptr[0]++) << 24) |
                     (*(ptr[1]++) << 16) |
                     (*(ptr[2]++) << 8 ) |
                     (*(ptr[3]++));