diff --git a/libavfilter/avf_showcwt.c b/libavfilter/avf_showcwt.c
index 85cb19103b..96b8841380 100644
--- a/libavfilter/avf_showcwt.c
+++ b/libavfilter/avf_showcwt.c
@@ -655,7 +655,7 @@ static int compute_kernel(AVFilterContext *ctx)
 
         memset(tkernel, 0, size * sizeof(*tkernel));
         for (int n = 0; n < size; n++) {
-            float ff, f = n-frequency;
+            float ff, f = n+0.5f-frequency;
 
             f = hsize - fabsf(f - hsize);
             ff = expf(-f*f*deviation);