diff --git a/video/out/filter_kernels.c b/video/out/filter_kernels.c
index a33fb9179f..cf681cc5db 100644
--- a/video/out/filter_kernels.c
+++ b/video/out/filter_kernels.c
@@ -240,7 +240,7 @@ static double kaiser(params *p, double x)
 {
     if (x > 1)
         return 0;
-    double i0a = 1.0 / bessel_i0(p->params[1]);
+    double i0a = 1.0 / bessel_i0(p->params[0]);
     return bessel_i0(p->params[0] * sqrt(1.0 - x * x)) * i0a;
 }