diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index 87cb093ed5..2c530d96a8 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -1186,8 +1186,8 @@ static void global_mv(DiracContext *s, DiracBlock *block, int x, int y, int ref)
     int *c      = s->globalmc[ref].perspective;
 
     int64_t m   = (1<<ep) - (c[0]*(int64_t)x + c[1]*(int64_t)y);
-    int64_t mx  = m * (int64_t)((A[0][0] * (int64_t)x + A[0][1]*(int64_t)y) + (1LL<<ez) * b[0]);
-    int64_t my  = m * (int64_t)((A[1][0] * (int64_t)x + A[1][1]*(int64_t)y) + (1LL<<ez) * b[1]);
+    int64_t mx  = m * (uint64_t)((A[0][0] * (int64_t)x + A[0][1]*(int64_t)y) + (1LL<<ez) * b[0]);
+    int64_t my  = m * (uint64_t)((A[1][0] * (int64_t)x + A[1][1]*(int64_t)y) + (1LL<<ez) * b[1]);
 
     block->u.mv[ref][0] = (mx + (1<<(ez+ep))) >> (ez+ep);
     block->u.mv[ref][1] = (my + (1<<(ez+ep))) >> (ez+ep);