diff --git a/libavfilter/vf_ciescope.c b/libavfilter/vf_ciescope.c
index 7c0cfed061..311696817d 100644
--- a/libavfilter/vf_ciescope.c
+++ b/libavfilter/vf_ciescope.c
@@ -842,7 +842,8 @@ rgb_to_xy(double rc,
     *z = m[2][0] * rc + m[2][1] * gc + m[2][2] * bc;
 
     sum = *x + *y + *z;
-
+    if (sum == 0)
+        sum = 1;
     *x = *x / sum;
     *y = *y / sum;
 }